Parlay Calculator

Build your calculation

Illustrative examples, not current offers: Illustrative: two 2.00 legs · Illustrative: two -110 legs · Illustrative: mixed formats

Hypothetical result

Enter odds for at least two legs and a positive stake to see your calculation.

Hypothetical calculation only. Assumes independent legs; odds-implied probability is not a forecast of the true chance of winning. Taxes, fees and promotions are excluded. This is not an executable parlay quote.

How to use the calculator

1. Enter a positive stake in USD and between 2 and 20 legs. A selection label is optional; each leg can use its own odds format.
2. Type odds manually or open the sports-market picker. The picker uses the available Polymarket feed, not a verified sportsbook odds feed. Missing quotes cannot be selected.
3. Read the hypothetical combined odds, odds-implied probability, return including stake and net profit. Every leg must be valid; incomplete entries suppress the result.
4. Use Calculate & save URL or Copy calculation link to preserve the inputs. A plain GET request to that URL returns the same calculation in initial HTML, without JavaScript or a market-data request.

What is a parlay? Odds and payout definitions

Parlay

A combined wager in which every included selection, or leg, must win under the applicable rules for the full return to be paid. This calculator models the multiplication of prices; it does not offer or place a wager.

Decimal odds

The total-return multiplier including the original stake. Decimal 2.00 represents $2 of return for each $1 staked if the selection wins.

American odds

Positive odds show profit per $100 staked; negative odds show the stake required for $100 of profit. Both +100 and -100 correspond to decimal 2.00.

Fractional odds

The profit-to-stake ratio. Fractional 3/2 means $3 of profit per $2 staked, equivalent to decimal 2.50.

Odds-implied probability

The reciprocal of decimal odds. Multiplying these price-derived probabilities assumes independence; it neither removes bookmaker margin nor estimates true win probability.

Total return and net profit

Total return includes the original stake. Net profit is total return minus that stake. Both are hypothetical all-legs-win figures before fees, taxes and promotions.

Formulas and calculation method

1. Convert each leg to decimal odds

For American odds A ≥ +100, d = 1 + A / 100. For A ≤ -100, d = 1 + 100 / |A|. For fractional odds N/M, d = 1 + N / M. Decimal input is used directly. Each leg has implied probability p = 1 / d.

2. Multiply the decimal prices

Combined decimal odds D = d1 × d2 × … × dn. The combined odds-implied probability is P = 1 / D, or p1 × p2 × … × pn under the independent-leg assumption. This does not adjust for correlation or remove vig.

3. Calculate return and profit

For stake S, total return R = S × D. Net profit = R - S. The calculator multiplies unrounded odds; presentation rounding is applied only to the displayed outputs, not before payout calculation.

4. Display combined American odds

If D ≥ 2, American odds = +100 × (D - 1). If 1 < D < 2, American odds = -100 / (D - 1). A parlay of strong favorites can therefore still have negative American odds.

How prediction-market prices are mapped

The feed supplies YES bestAsk and YES bestBid in 0–1 units. YES uses bestAsk; NO uses 1 - bestBid, a derived complementary-bid price, not a separately verified NO ask. For valid price q strictly between 0 and 1, the hypothetical decimal multiplier is 1 / q. Midpoints, rounded display odds, missing quotes and fabricated fallback prices are never substituted.

Worked examples

Illustrative: two 2.00 legs

2.00 × 2.00 = 4.00, equivalent to American +300. The odds-implied probability is 1 / 4 = 25%. A $10 stake gives a hypothetical $40.00 total return and $30.00 net profit.

Illustrative: two -110 legs

Each -110 price is 1 + 100 / 110 = 1.909090… in decimal odds. Multiplying the unrounded prices gives 3.644628… (displayed as 3.64, or American +264), with about 27.4376% implied probability. A $10 stake gives $36.45 total return and $26.45 net profit, not the result of multiplying a rounded 3.64.

Illustrative: mixed formats

+100 becomes 2.00 and 3/2 becomes 2.50. Then 2.00 × 2.50 × 1.50 = 7.50, or +650 American odds. A $10 stake gives $75.00 total return and $65.00 net profit. These are made-up prices for arithmetic, not current games or offers.

Assumptions and limitations

Hypothetical calculation only. Assumes independent legs; odds-implied probability is not a forecast of the true chance of winning. Taxes, fees and promotions are excluded. This is not an executable parlay quote.

Polymarket selections are prediction-market prices, not verified sportsbook odds. Multiplying their implied odds does not show that Polymarket or another venue offers the parlay. Buying separate positions does not reproduce the calculated all-or-nothing parlay payout.

Known duplicates and opposing sides of the same feed market cannot be combined. Different selections from the same event trigger a correlation warning. Event identifiers cannot reveal every relationship, and manual or URL-restored inputs must be checked by the user.

Selected prices are captured snapshots. The page shows the feed's retrieval time, not an exchange quote timestamp or an execution guarantee. A background refresh never silently changes selected prices. Edited sourced prices are marked as manual overrides.

Feed coverage can be cached, partial, unknown or unavailable. Missing quotes remain unavailable; manual calculations and no-JavaScript calculation URLs do not depend on the feed.

Inputs use plain finite numbers without currency signs, commas or exponent notation. Use 2–20 legs and a positive stake of at most $1,000,000. Text, URL and result-size limits prevent excessive or unsafe calculations; unsupported inputs show errors instead of a partial result.

Number fields are limited to 64 characters, selection labels to 80 and URL query strings to 8,192. Raw odds components and per-leg decimal multipliers are limited to 1,000,000,000,000; calculated output magnitudes are limited to 1,000,000,000,000,000.

Decimal odds are displayed to two places, American odds to the nearest whole number, and money to cents. Probabilities use up to four decimal places with honest bounds for values too close to zero or 100%. Inputs and intermediate calculations are not rounded to these display precisions.

Frequently asked questions

How do I calculate a parlay payout?

Convert every leg to decimal odds, multiply those decimal prices together, then multiply by the stake. That is the hypothetical total return including stake. Subtract the stake to obtain net profit.

Can I mix American, decimal and fractional odds?

Yes. Each of the 2–20 legs has its own format. The interactive format control converts a valid price rather than reinterpreting its number. All prices are converted to decimal odds internally before multiplication.

Is implied probability the true chance my parlay wins?

No. It is the reciprocal of the combined decimal price, under an independent-leg assumption. It can include margin and other pricing effects, and is not an independently verified forecast or a guarantee.

Can I use same-game selections?

Different selections from the same known feed event produce a prominent correlation warning. Their true joint probability can differ substantially from multiplying individual probabilities. This calculator does not price same-game parlays or adjust for correlation. Opposing sides of the same market and duplicates are blocked.

What happens if a leg is voided or pushes?

Rules depend on the provider and product. Some ordinary parlays remove a voided leg, mathematically treating it as decimal 1.00, and recalculate the remaining legs; same-game products and prediction markets may have different rules. This calculator is not a settlement engine. Check the provider's rules; you can remove a leg to explore the remaining calculation when at least two valid legs remain.

Are the selectable feed prices sportsbook parlay quotes?

No. They are available Polymarket prediction-market snapshots. YES uses the ask; NO uses the complement of the YES bid. The multiplied payout is hypothetical, is not an executable quote, and cannot be reproduced simply by buying those positions separately.

Does the calculator work without JavaScript or signing in?

Yes. The visible GET form and numbered calculation URLs return entered prices, results or validation errors in initial HTML without signing in, using a wallet, or requesting market data. Choosing current feed selections is an optional JavaScript enhancement.

Calculation URLs and no-JavaScript use

Send a read-only GET request to /parlay-calculator with stake and contiguous numbered oddsN and formatN fields for N = 1 through 20. Supply 2–20 legs. Format values are american, decimal and fractional; include formatN explicitly for each leg. Optional labelN fields carry user-supplied selection text only.

Example: /parlay-calculator?stake=10&format1=american&odds1=-110&format2=american&odds2=-110 returns the entered prices, $36.45 total return and $26.45 profit in HTML. No REST/JSON calculation API, MCP tool or AI-provider integration is needed.

Percent-encode special characters: +100 should be %2B100 and 3/2 can be 3%2F2. The form and Copy calculation link control handle encoding. Repeated fields, unsupported formats, gaps, out-of-range leg numbers and excessive input lengths produce validation errors rather than silently dropping legs.

Inputs restored from a calculation URL are user-supplied snapshots, not reverified live quotes. Source identities and retrieval times are not certified or restored by the link. Check any same-event relationships yourself.

Only the clean English reference page is indexable. Calculation URLs are noindex, follow and canonicalize to the clean page; browsing assistants can still fetch and read their actual HTML results. Bookmark a link, reload it or use browser back/forward to restore saved inputs.

/parlay-calculator?stake=10&format1=american&odds1=-110&format2=american&odds2=-110