How to Convert Odds: Complete Guide

Whether you are comparing prices between sportsbooks, trying to understand international odds formats, or calculating your potential profit, knowing how to convert odds is an essential skill for any sports bettor. This complete guide walks you through every odds conversion formula step by step, with clear examples and ready-to-use tables.

If you just want fast conversions, use the Odds Converter Calculator below. The rest of this guide explains the maths behind each conversion so you can do it manually when needed.

What Does It Mean to Convert Odds?

Sports betting odds represent the same information in different formats. Depending on where you are betting or which sportsbook you use, you will encounter three main odds formats:

American odds (also called moneyline odds) are the standard in the United States. They display as positive numbers like +200 or negative numbers like -110. Positive odds show how much profit you win on a 100 dollar stake, while negative odds show how much you must stake to win 100 dollars in profit.

Decimal odds are common across Europe, Australia, and most international sportsbooks. They show your total return including your stake. For example, decimal odds of 2.50 mean a 100 dollar bet returns 250 dollars total (150 dollars profit plus your 100 dollar stake back).

Fractional odds are traditional in the United Kingdom and remain popular for horse racing. They display as fractions like 3/1 (read as three to one) or 5/2 (five to two). The fraction shows profit relative to stake: 3/1 means you win 3 dollars profit for every 1 dollar staked.

Converting odds means translating between these formats so you can compare prices across different sportsbooks, calculate your potential returns consistently, and understand implied probability. When the Buffalo Bills are listed at -150 on one book and 1.67 on another, you need to know these represent the same price before making a decision.

Understanding implied probability is also part of the conversion picture. Every odds format can be translated into a percentage that represents the bookmakers estimate of how likely an outcome is to happen. This probability perspective helps you spot value and compare markets more effectively.

Use Our Free Odds Converter Calculator

The fastest way to convert betting odds is to use a dedicated calculator. Our Odds Converter Calculator instantly converts between American, Decimal, Fractional, and implied probability formats.

Simply select your input format, enter the odds, and see the equivalent values across all other formats. You can also enter a stake amount to see your potential profit and total return.

The calculator handles all the formulas automatically, including the different calculations required for positive and negative American odds. Try converting a few examples as you read through the guide to reinforce the concepts.

How to Convert American Odds to Decimal, Fractional, and Probability

American odds are the format most US bettors see daily. Converting them requires different formulas depending on whether the odds are positive or negative.

Positive American odds (like +200, +150, +300) indicate how much profit you win on a 100 dollar stake. The plus sign means the outcome is considered less likely than even money.

Negative American odds (like -110, -150, -200) indicate how much you must stake to win 100 dollars profit. The minus sign means the outcome is considered more likely than even money.

American to Decimal Odds Conversion Formula

For positive American odds, the formula is:

Decimal = (American / 100) + 1

For negative American odds, the formula is:

Decimal = (100 / Absolute value of American) + 1

Let us work through some examples:

Converting +200 to Decimal: Decimal = (200 / 100) + 1 = 2 + 1 = 3.00

Converting +150 to Decimal: Decimal = (150 / 100) + 1 = 1.5 + 1 = 2.50

Converting -110 to Decimal: Decimal = (100 / 110) + 1 = 0.909 + 1 = 1.91

Converting -150 to Decimal: Decimal = (100 / 150) + 1 = 0.667 + 1 = 1.67

Once you have the decimal equivalent, converting to fractional is straightforward: subtract 1 from the decimal to get the profit multiple, then express it as a fraction.

American Odds to Implied Probability

For positive American odds, the implied probability formula is:

Probability = 100 / (American + 100)

For negative American odds, the formula is:

Probability = Absolute value of American / (Absolute value of American + 100)

Converting +200 to probability: Probability = 100 / (200 + 100) = 100 / 300 = 0.333 = 33.3%

Converting -110 to probability: Probability = 110 / (110 + 100) = 110 / 210 = 0.524 = 52.4%

Converting -150 to probability: Probability = 150 / (150 + 100) = 150 / 250 = 0.60 = 60%

This table shows common American odds with their Decimal, Fractional, and implied probability equivalents:

American	Decimal	Fractional	Implied Probability
+500	6.00	5/1	16.7%
+300	4.00	3/1	25%
+200	3.00	2/1	33.3%
+150	2.50	3/2	40%
+100	2.00	1/1	50%
-110	1.91	10/11	52.4%
-150	1.67	2/3	60%
-200	1.50	1/2	66.7%
-300	1.33	1/3	75%

How to Convert Decimal Odds to American, Fractional, and Probability

Decimal odds are popular on European and international sportsbooks. Many bettors prefer this format because calculations are simpler, especially for parlays where you multiply the decimal odds together.

The key to understanding decimal odds: they represent your total return per unit staked, including your original stake. Decimal odds of 2.00 are even money, meaning you double your money if you win.

Decimal to Implied Probability

The simplest conversion. Just divide 1 by the decimal odds:

Probability = 1 / Decimal

Converting 2.50 to probability: Probability = 1 / 2.50 = 0.40 = 40%

Converting 1.91 to probability: Probability = 1 / 1.91 = 0.524 = 52.4%

Converting 1.50 to probability: Probability = 1 / 1.50 = 0.667 = 66.7%

Decimal to American Odds

The formula depends on whether the decimal odds are above or below 2.00.

For decimal odds of 2.00 or higher (plus money in American):

American = (Decimal - 1) x 100

For decimal odds below 2.00 (minus money in American):

American = -100 / (Decimal - 1)

Converting 3.00 to American: American = (3.00 - 1) x 100 = 2 x 100 = +200

Converting 2.50 to American: American = (2.50 - 1) x 100 = 1.5 x 100 = +150

Converting 1.50 to American: American = -100 / (1.50 - 1) = -100 / 0.50 = -200

Converting 1.91 to American: American = -100 / (1.91 - 1) = -100 / 0.91 = -110

Decimal to Fractional Odds

Subtract 1 from the decimal to get the profit multiple, then express as a fraction:

Fractional = (Decimal - 1) as a fraction

Converting 3.00 to Fractional: 3.00 - 1 = 2.00, expressed as 2/1

Converting 2.50 to Fractional: 2.50 - 1 = 1.50, expressed as 3/2

Converting 1.50 to Fractional: 1.50 - 1 = 0.50, expressed as 1/2

Decimal	American	Fractional	Implied Probability
1.50	-200	1/2	66.7%
1.67	-150	2/3	60%
1.91	-110	10/11	52.4%
2.00	+100	1/1	50%
2.50	+150	3/2	40%
3.00	+200	2/1	33.3%
4.00	+300	3/1	25%

How to Convert Fractional Odds to American, Decimal, and Probability

Fractional odds remain common in UK horse racing and some traditional bookmakers. US bettors may encounter them when betting on international horse racing or using UK-based sportsbooks.

Fractional odds like 3/1 mean you win 3 dollars profit for every 1 dollar staked. The numerator (top number) represents potential profit, the denominator (bottom number) represents the stake.

Fractional to Decimal Odds

Add the numerator and denominator together, then divide by the denominator:

Decimal = (Numerator + Denominator) / Denominator

Alternatively: Decimal = (Fractional value) + 1

Converting 3/1 to Decimal: Decimal = (3 + 1) / 1 = 4 / 1 = 4.00

Converting 5/2 to Decimal: Decimal = (5 + 2) / 2 = 7 / 2 = 3.50

Converting 1/4 to Decimal: Decimal = (1 + 4) / 4 = 5 / 4 = 1.25

Fractional to Implied Probability

Divide the denominator by the sum of numerator and denominator:

Probability = Denominator / (Numerator + Denominator)

Converting 3/1 to probability: Probability = 1 / (3 + 1) = 1 / 4 = 0.25 = 25%

Converting 1/2 to probability: Probability = 2 / (1 + 2) = 2 / 3 = 0.667 = 66.7%

Converting 4/5 to probability: Probability = 5 / (4 + 5) = 5 / 9 = 0.556 = 55.6%

Fractional to American Odds

First convert to decimal, then apply the decimal to American formula. Or use these direct approaches:

For fractional odds of 1/1 or higher (plus money):

American = (Numerator / Denominator) x 100

For fractional odds below 1/1 (minus money):

American = -100 / (Numerator / Denominator)

Converting 3/1 to American: American = (3 / 1) x 100 = +300

Converting 5/2 to American: American = (5 / 2) x 100 = 2.5 x 100 = +250

Converting 1/4 to American: Since 1/4 is less than 1/1, this is minus money. American = -100 / (1/4) = -100 / 0.25 = -400

Fractional	Decimal	American	Implied Probability
1/4	1.25	-400	80%
1/2	1.50	-200	66.7%
4/5	1.80	-125	55.6%
1/1	2.00	+100	50%
5/4	2.25	+125	44.4%
3/1	4.00	+300	25%
5/1	6.00	+500	16.7%
10/1	11.00	+1000	9.1%

Implied Probability: Converting Odds into Percentage Chance

Implied probability is perhaps the most important concept in odds conversion. It translates any odds format into a percentage that represents how likely the sportsbook thinks an outcome is.

Understanding implied probability allows you to compare bookmaker odds to your own assessment of an events likelihood. This comparison is the foundation of value betting.

Here are the formulas for each format:

From Decimal odds: Probability = 1 / Decimal

From Fractional odds: Probability = Denominator / (Numerator + Denominator)

From positive American odds: Probability = 100 / (American + 100)

From negative American odds: Probability = Absolute value of American / (Absolute value of American + 100)

Common Implied Probability Examples

What percentage is +200 odds? Probability = 100 / (200 + 100) = 100 / 300 = 33.3%

This means the bookmaker believes there is roughly a 1 in 3 chance of this outcome occurring.

What is -110 as a percentage? Probability = 110 / (110 + 100) = 110 / 210 = 52.4%

The standard -110 odds on spreads and totals imply a 52.4% chance. The extra 2.4% above 50% is the bookmakers edge (the vig or juice).

What probability does +150 represent? Probability = 100 / (150 + 100) = 100 / 250 = 40%

Using Implied Probability for Value Betting

If you estimate that a team has a 45% chance to win but the odds are +200 (implying only 33.3%), you have found potential value. Your estimate suggests the fair odds should be closer to +122.

Our Implied Probability Calculator can help you quickly convert any odds to probability. For a deeper dive into how to use this information strategically, see our guide to implied probability in sports betting.

Note that implied probabilities from a sportsbook always add up to more than 100% because of the vig. For a two-way market with both sides at -110, the implied probabilities total 104.8% (52.4% + 52.4%). The extra 4.8% is the bookmakers margin. You can use a vig calculator to remove the juice and find true fair odds.

Odds Conversion Tables and Cheat Sheets

Sometimes you just need a quick reference without doing calculations. These comprehensive tables cover the most common odds you will encounter.

American	Decimal	Fractional	Implied Prob
-1000	1.10	1/10	90.9%
-500	1.20	1/5	83.3%
-400	1.25	1/4	80%
-300	1.33	1/3	75%
-250	1.40	2/5	71.4%
-200	1.50	1/2	66.7%
-175	1.57	4/7	63.6%
-150	1.67	2/3	60%
-130	1.77	10/13	56.5%
-120	1.83	5/6	54.5%
-110	1.91	10/11	52.4%
-105	1.95	20/21	51.2%
+100	2.00	1/1	50%
+105	2.05	21/20	48.8%
+110	2.10	11/10	47.6%
+120	2.20	6/5	45.5%
+130	2.30	13/10	43.5%
+150	2.50	3/2	40%
+175	2.75	7/4	36.4%
+200	3.00	2/1	33.3%
+250	3.50	5/2	28.6%
+300	4.00	3/1	25%
+400	5.00	4/1	20%
+500	6.00	5/1	16.7%
+750	8.50	15/2	11.8%
+1000	11.00	10/1	9.1%

Keep this table bookmarked for quick reference when you see an odds format you are not familiar with. For instant conversions of any specific odds, use the Odds Converter Calculator above.

How to Convert Odds in Excel and Google Sheets

For bettors who track their wagers or build their own models, having odds conversion formulas in a spreadsheet is invaluable. Here are ready-to-use formulas for Excel and Google Sheets.

American to Decimal Conversion

If your American odds are in cell A2, use this formula:

=IF(A2 greater than 0, (A2/100)+1, (100/ABS(A2))+1)

This formula checks whether the odds are positive or negative and applies the appropriate conversion.

American to Implied Probability

=IF(A2 greater than 0, 100/(A2+100), ABS(A2)/(ABS(A2)+100))

The result will be a decimal between 0 and 1. Format the cell as a percentage or multiply by 100 for a percentage value.

Decimal to Implied Probability

=1/A2

This simple formula gives you the probability as a decimal.

Decimal to American

=IF(A2 greater than or equal to 2, (A2-1)*100, -100/(A2-1))

Fractional to Decimal

If your fractional odds are in two cells (numerator in A2, denominator in B2):

=(A2+B2)/B2

Or simply:

=(A2/B2)+1

Sample Spreadsheet Layout

Set up your spreadsheet with these columns:

• Column A: Sportsbook name
• Column B: Market or bet type
• Column C: American odds (input)
• Column D: Decimal odds (formula)
• Column E: Implied probability (formula)
• Column F: Your estimated probability (input)
• Column G: Edge calculation (formula comparing E and F)

This layout lets you input odds from any sportsbook, instantly see the decimal equivalent and implied probability, and compare against your own estimates to identify potential value.

Note: In the formulas above, replace the words greater than with the actual greater than symbol and less than with the less than symbol. Spreadsheet formulas use these mathematical comparison operators directly.

How to Use the OddsIndex Odds Converter Calculator

Our Odds Converter is designed for speed and accuracy. Here is a step-by-step walkthrough:

Step 1: Select Your Input Format Choose whether you are entering American, Decimal, Fractional, or probability.

Step 2: Enter Your Odds Type in the odds exactly as you see them. For American odds, include the plus or minus sign. For fractional odds, enter as a decimal (e.g., enter 3 for 3/1, or use the fraction format if supported).

Step 3: View All Conversions The calculator instantly displays the equivalent odds in all other formats plus the implied probability.

Step 4: Optional - Enter a Stake Input a stake amount to see your potential profit and total return for each format.

Example Conversions

Example 1: NFL Spread at -110 Enter -110 in American format. The calculator shows:

• Decimal: 1.91
• Fractional: 10/11
• Implied Probability: 52.4%
• With 100 dollar stake: 90.91 dollar profit, 190.91 dollar total return

Example 2: NBA Moneyline Underdog at +200 Enter +200 in American format. The calculator shows:

• Decimal: 3.00
• Fractional: 2/1
• Implied Probability: 33.3%
• With 50 dollar stake: 100 dollar profit, 150 dollar total return

Example 3: Horse Racing at 3/1 Enter 3/1 in Fractional format. The calculator shows:

• American: +300
• Decimal: 4.00
• Implied Probability: 25%

Example 4: Soccer Match at 1.50 Decimal Enter 1.50 in Decimal format. The calculator shows:

• American: -200
• Fractional: 1/2
• Implied Probability: 66.7%

Using the calculator is faster and more reliable than manual calculations, especially when comparing multiple sportsbooks quickly.

Using Odds Conversion to Find Value Bets

Understanding odds conversion is about more than just translating formats. It is the first step toward becoming a more analytical bettor.

When you convert odds to implied probability, you can compare the bookmakers estimate to your own assessment. If you believe the Kansas City Chiefs have a 55% chance to beat the spread but the -110 odds only imply 52.4%, you have identified potential value.

The formula for identifying value is straightforward:

Edge = Your estimated probability - Implied probability

If your edge is positive, the bet has theoretical value. If your edge is negative, the sportsbook has the advantage at those odds.

This approach ties into broader concepts like expected value betting. For a complete guide on how to use probability and odds to make smarter bets, see our Expected Value Betting Guide.

Additionally, comparing odds across multiple sportsbooks (line shopping) is easier when you can quickly convert to a common format. A line at -108 on one book versus -112 on another may not seem like much, but converting to implied probability (51.9% vs 52.8%) shows the real difference.

Common Mistakes When Converting Odds

Even experienced bettors make conversion errors. Here are the most common mistakes to avoid:

Confusing positive and negative American odds formulas. The formulas are different for plus and minus odds. Using the wrong formula gives incorrect results. Always check the sign before applying a formula.

Forgetting to subtract 1 when converting Decimal to Fractional. Decimal odds include your stake, fractional odds show profit only. A decimal of 2.50 becomes 3/2 (or 1.50/1), not 2.50/1.

Treating implied probability as a guaranteed outcome. Implied probability is the bookmakers estimate baked into the odds. It is not a prediction of what will happen. A 60% implied probability means the bettor loses 40% of the time at those odds.

Not accounting for vig when comparing markets. A -110/-110 spread market has 4.8% vig. When comparing odds between books, remember that implied probabilities include the bookmakers margin. Use no-vig calculations for true apples-to-apples comparisons.

Rounding errors in manual calculations. Small rounding differences can add up, especially in parlays. When precision matters, use a calculator rather than mental math.

Using the wrong fraction simplification. When converting to fractional odds, not all decimals simplify to clean fractions. 1.91 becomes approximately 10/11, not 9/10.

The easiest way to avoid these mistakes is to use the Odds Converter Calculator for any conversions that matter.

Frequently Asked Questions

How do you calculate odds manually?

To convert odds manually, use the appropriate formula for your starting format. For American to Decimal: if positive, divide by 100 and add 1; if negative, divide 100 by the absolute value and add 1. For Decimal to probability, divide 1 by the decimal odds. For Fractional to Decimal, add the numerator and denominator then divide by the denominator. Practice with a few examples and the patterns become intuitive.

What is the formula for converting odds to percentage?

For Decimal odds, the implied probability formula is 1 divided by the decimal. For positive American odds, use 100 divided by (American odds plus 100). For negative American odds, use the absolute value of the American odds divided by (absolute value plus 100). For Fractional odds, divide the denominator by the sum of numerator and denominator.

What percentage is +200 odds?

Plus 200 American odds represent a 33.3% implied probability. The calculation is 100 divided by (200 plus 100), which equals 100 divided by 300, or 0.333. This means the sportsbook estimates roughly a 1 in 3 chance of this outcome occurring.

What is 3/1 in American odds?

Fractional odds of 3/1 convert to plus 300 in American format. To convert, multiply the fraction (3 divided by 1 equals 3) by 100, giving you plus 300. In decimal format, 3/1 equals 4.00, and the implied probability is 25%.

What is 1.5 in moneyline odds?

Decimal odds of 1.50 convert to minus 200 in American moneyline format. Since 1.50 is below 2.00, you use the negative American formula: minus 100 divided by (1.50 minus 1), which equals minus 100 divided by 0.50, or minus 200. The implied probability is 66.7%.

Why are American odds negative?

American odds are negative when the outcome is considered more likely than even money (more than 50% probability). Negative odds indicate how much you must stake to win 100 dollars profit. For example, minus 150 means you must risk 150 dollars to win 100 dollars profit. The more negative the odds, the heavier the favorite.

What does -110 mean in betting?

Minus 110 is the standard odds for point spreads and totals in American sports betting. It means you must bet 110 dollars to win 100 dollars profit (or 11 dollars to win 10 dollars). The implied probability is 52.4%. The extra 2.4% above 50% represents the sportsbooks commission, known as the vig or juice.

How do you convert odds in Excel or Google Sheets?

Use conditional formulas that check whether American odds are positive or negative. For American to Decimal, the formula is: IF the odds are greater than 0, then (odds divided by 100) plus 1, otherwise (100 divided by absolute value of odds) plus 1. For American to implied probability: IF greater than 0, then 100 divided by (odds plus 100), otherwise absolute value divided by (absolute value plus 100).

Understanding Odds Formats Makes You a Better Bettor

Knowing how to convert odds is not just a mathematical exercise. It is a fundamental skill that helps you compare prices across sportsbooks, calculate your potential returns accurately, and understand the implied probabilities behind every betting line.

Whether you prefer doing quick mental conversions, referencing the tables in this guide, or using our Odds Converter Calculator, the key is becoming comfortable with all three major odds formats. For a complete walkthrough of the calculator features, see our Odds Converter Calculator guide.

As you develop your betting approach, this knowledge forms the foundation for more advanced concepts like expected value, vig calculation, and line shopping. Understanding what the odds really mean is the first step toward betting with an edge rather than just guessing.