This article explains how to calculate FanDuel moneyline odds and how to use a fanduel odds calculator to convert those odds into implied probability, decimal and fractional formats. It also shows a practical de-vig method so you can estimate fair probabilities and compare prices across markets. The guide is example-driven and includes spreadsheet-ready formulas, payout math and validation checks you can run in minutes. It assumes basic familiarity with odds but walks through each conversion step so you can replicate the calculations yourself.

Learn the exact American-to-probability formulas used across the industry and how to implement them.

Use a simple normalization method to remove vig and estimate fair odds for model comparison.

Copy-paste spreadsheet templates and sanity checks help you validate calculations quickly.

What FanDuel moneyline odds mean: definition and context

American (moneyline) odds explained

FanDuel displays moneyline prices in the American format, where favorites are shown with a negative number and underdogs with a positive number; a fanduel odds calculator uses those American values as its input to convert to probability and returns FanDuel help center.

American odds express how much you must stake or can win relative to 100 units, and the same convention underlies the standard formulas used to compute implied probability.

Convert American odds to implied probability, decimal and fractional and compute payout

Implied probability
Decimal odds
Fractional odds
Payout

Use absolute value for negative moneylines

Why implied probability matters for bettors

Implied probability translates a quoted moneyline into the market view of an event's chance; that conversion is the first step for any quantitative comparison or value-seeking exercise, and it is the key number a fanduel odds calculator should report alongside alternate formats Investopedia implied probability guide.

Knowing the implied probability helps you compare a listed price against your own model or intuition and decide whether the market is offering value.

Quick calculator workflow: how to use a fanduel odds calculator (step by step)

Inputs required (odds, stake, market type)

Start with three simple inputs: the American odds as shown on FanDuel, a stake if you want payout figures, and whether you plan to de-vig the market before interpreting results.

For computational accuracy remember to treat negative moneylines by absolute value when applying formulas and to note whether the market is two-way or three-way because overround calculation changes with market structure Action Network odds conversion.

Step-by-step: enter American odds, get implied probability, decimal, fractional - fanduel odds calculator

Enter the American moneyline, e.g., +250 or -140.
Compute implied probability using the appropriate formula for the sign.

Try the FundedPlays Challenges for structured practice

Try the worked example below in this section to confirm the calculator returns the shown probabilities and conversions.

View FundedPlays Challenges

After you compute implied probability, convert that value into decimal and fractional odds for easier model comparisons or display preferences.

Finally, if you want to estimate fair prices, include a de-vig step to normalize implied probabilities across all market outcomes.

How to convert American odds to decimal and fractional formats

Formulas for positive and negative American odds

For positive American odds +A use decimal = 1 + A/100 and fractional = A/100; for negative odds -A use decimal = 1 + 100/A and fractional = 100/A, where A is the absolute value of the number shown on the moneyline Odds reference.

Worked examples with calculation results

Example 1, a positive moneyline: +250 converts to decimal 1 + 250/100 = 3.5 and fractional 250/100 = 5/2; a simple fanduel odds calculator should show these three aligned formats for clarity.

How do you convert FanDuel moneyline odds into implied probability and fair odds?

Use the standard American-to-probability formulas, convert to decimal or fractional as needed, compute the market overround by summing implied probabilities, then normalize each probability by dividing by the overround to estimate fair odds before reconverting to the desired format.

Example 2, a negative moneyline: -140 converts to decimal 1 + 100/140 = 1.714285... and fractional 100/140 which simplifies to 5/7, and a calculator should format decimal odds to a reasonable rounding precision for display.

Why market odds differ from fair odds: vig and overround

What bookmaker margin (vig or overround) is

Sportsbooks embed a margin, often called vig or overround, that causes the sum of implied probabilities for a market to exceed 100 percent; detecting that excess is the first step to estimating fair probabilities Pinnacle margin guide.

That extra percentage point total inflates quoted probabilities and compresses returns relative to a zero-margin market, so a fanduel odds calculator that compares model probabilities to market prices should offer a de-vig option.

How the sum of implied probabilities reveals the overround

Compute each selection's implied probability, add them and compare the total to 100 percent; the surplus is the market overround and shows how much margin is embedded in the prices.

For a three-way market the same approach applies, but you should be careful to include all listed outcomes when summing implied probabilities to get an accurate overround measure.

De-vig method: turning FanDuel prices into fair probabilities

Normalize implied probabilities by dividing by the overround

Practical de-vig follows three steps: compute each implied probability from the American odds, sum those probabilities to get the total overround, then divide each implied probability by the total to produce normalized fair probabilities; this normalization is a straightforward method for a fanduel odds calculator to estimate fair prices Smarkets overround explanation.

Funded Plays Challenges page

View FundedPlays Challenges

Once normalized, reconvert the fair probabilities back into decimal or American odds for direct comparison with the original market quotes; reconversion makes it easier to see the effect of de-vig on apparent value.

Reconvert normalized probabilities back into American, decimal or fractional odds

To reconvert a normalized probability p to decimal use 1/p; to convert to American, invert the earlier formulas and apply the sign convention for favorites and underdogs so that you get a standard moneyline representation for each normalized probability.

A simple two-outcome worked example below shows the before and after odds so you can confirm your calculator handles reconversion correctly.

Calculating payouts on FanDuel: stake, profit and total return

Payout formulas for +A and -A

Full frame spreadsheet screenshot showing American odds implied probability normalized probability and payouts for a fanduel odds calculator in Funded Plays dark palette

When you stake S at a positive moneyline +A the profit equals S times A/100 and the total return equals S times 1 + A/100; for a negative moneyline -A the profit equals S times 100/A and the total return equals S times 1 + 100/A, which are the formulas a fanduel odds calculator must implement for payout fields Implied probability reference.

Using these formulas makes it easy to validate that the payout numbers shown by a calculator match FanDuel's displayed returns for equivalent stakes and odds.

Examples showing stake, profit and total return

Example positive stake: S = 10 units at +250 gives profit 10 * 250/100 = 25 units and total return 35 units.

Example negative stake: S = 10 units at -140 gives profit 10 * 100/140 = 7.142857... units and total return 17.142857... units; round as appropriate for display and to match typical sportsbook presentation.

Practical tools: using a spreadsheet or simple fanduel odds calculator

Template spreadsheet fields and formulas

Suggested columns: American odds, Sign-handled A, Implied probability formula, Decimal odds, Fractional odds, Normalized probability, De-vig decimal, Stake, Profit, Total return; each formula should match the expressions given earlier so the spreadsheet reproduces calculator behavior exactly Action Network conversion guide.

For absolute value use a cell formula like ABS(value) when handling negative moneylines and keep a separate column for the market overround to make de-vig steps transparent to readers or auditors.

Quick built-in calculator options to validate results

Many spreadsheet tools include simple math functions that are enough to build a fanduel odds calculator; implement the formulas exactly and test with the worked examples in this guide to verify correctness. Try the Covers odds converter Covers odds converter or an implied probability tool like OmniCalculator.

Always test edge cases such as heavy favorites and long shots to ensure your spreadsheet does not produce divide-by-zero errors or unexpected rounding behavior.

How to decide when to adjust (or not) for vig

When market odds are fine as-is

If you are placing a small recreational wager for entertainment, using market odds without de-vigging is acceptable because the practical difference after vig may be minor for single bets.

For systematic comparison across books or when your model produces tight margins, normalizing probabilities can materially change perceived value and is worth the additional step Pinnacle margin guide.

When you should de-vig for comparison or value detection

De-vig when you compare markets, search for value edges, or feed probabilities into an automated model that assumes fair prices; de-vigging reduces the noise introduced by differing margin levels across books.

Remember that vig levels vary by event and market, so treat de-vigged outputs as estimates rather than exact true probabilities.

Common mistakes to avoid when using a fanduel odds calculator

Sign errors and forgetting absolute values

Typical mistakes include failing to use absolute value for negative moneylines when applying formulas and mixing up profit versus total return; these sign errors produce incorrect probabilities or payout numbers and are easy to detect with the sanity checks in this guide Implied probability guide.

Always keep a test case of a known conversion handy to validate any new implementation.

Ignoring vig and misreading payouts

Assuming quoted implied probabilities are fair without checking for overround can lead to overestimating value; include an overround calculation and a reconversion test to spot errors quickly.

When you calculate payouts, label columns clearly so profit and total return are not confused during reporting or downstream calculations.

Practical scenarios: three worked examples using FanDuel odds

Two-way market example with de-vig

Example 1, a two-way tennis match: Player A -150, Player B +120. Implied probabilities before de-vig are computed per the moneyline formulas and then summed to produce the overround; the de-vig step divides each implied probability by that total so you can see fair probabilities after normalization Smarkets overround explanation.

Reconvert the normalized probabilities to decimal and American to observe how the favorite and underdog prices change once margin is removed.

Three-way market example and reconversion

Example 2, a soccer match with home, draw, away prices: convert each American or decimal listing to implied probability, sum to get the market overround, then normalize and reconvert so the post-de-vig American odds reflect fairer prices for model comparison.

Document the intermediate probabilities and the overround so anyone using your fanduel odds calculator can reproduce the numbers and audit the de-vig step.

Payout check for a negative favorite and a positive underdog

Example 3, stake checks: for a 20 unit stake at -200 compute profit and total return, and for a 5 unit stake at +300 compute profit and total return using the payout formulas; these spot checks confirm payout fields behave as expected Action Network payout reference.

Compare those numbers to FanDuel's displayed returns for identical inputs as an additional validation step.

A short checklist: validate your fanduel odds calculator results

Quick checks you can run in under a minute

Sanity checks include confirming the sum of implied probabilities exceeds 100 when vig is present, reconverting decimal odds back to American to verify formulas, and testing payout math with small known stakes.

Also ensure negative moneylines are converted using absolute value and that rounding rules are consistent across your outputs.

Common formula sanity tests

Keep a table of known conversions such as +250, -140 and standard decimal equivalents to run against any new implementation and store those test cases with timestamps.

If results differ from expected, check for a misplaced sign, an omitted absolute value call or a rounding step executed too early in the calculation sequence.

Advanced tips and when to automate the calculation

Batch de-vig for many markets

When you analyze multiple markets, batch de-vigging lets you compare vig patterns across a season or sport by normalizing probabilities for thousands of events and then aggregating differences by market type Pinnacle margin guide.

Store source odds, timestamps and market metadata to allow reproducibility and to investigate changes in vig over time.

Integrating odds conversion into analytics pipelines

Automate the conversion formulas and de-vig steps in your data pipeline, but schedule spot checks and holdback samples to guard against silent errors introduced by feed changes or data formatting issues.

Keep model dependence on de-vig assumptions explicit and document the method used so downstream decisions are traceable.

Summary: using a fanduel odds calculator responsibly

Key takeaways

Core formulas are simple: use the standard American-to-probability conversions, convert to decimal or fractional for display, and normalize implied probabilities by the overround to estimate fair odds; these steps are the backbone of any valid fanduel odds calculator Implied probability reference.

Always treat de-vigged outputs as estimates and use them to inform decisions rather than as guarantees, and remember that FanDuel prices include a margin like other books so direct comparison without normalization can be misleading.

References and where to read more

Authoritative references used in this guide

Primary resources for formulas and vig methods include Investopedia, Pinnacle, Smarkets, Action Network, Wikipedia and FanDuel help; check those sources directly for the underlying explanations and examples.

Save example calculations and test cases so you can replicate key steps when updating your own fanduel odds calculator or troubleshooting differences between markets.

What formula converts American odds to implied probability?

For positive odds +A use p = 100/(A + 100); for negative odds -A use p = A/(A + 100) with A as the absolute value.

When should I de-vig FanDuel odds?

De-vig when you compare books, search for model value or run analytics; for casual single bets de-vigging is often unnecessary.

How do I check my calculator payouts?

Test payouts with known stakes such as 10 units at +250 and 10 units at -140 and confirm profit and total return match the formulas.

Use the worked examples and checklist in this guide to validate any fanduel odds calculator you build or use, and remember to treat de-vigged prices as estimates for comparison rather than absolute truths. Keep test cases and timestamps with your calculations so you can audit and reproduce results later.