How do you calculate parlay odds?

Convert each leg to a decimal multiplier, then multiply them together. Three legs at 2.00, 1.67 and 2.08 give a combined 6.95 — a $50 stake returns about $347.

What is the real chance my parlay hits?

Multiply each leg's implied probability. Three 50% legs is 0.5 × 0.5 × 0.5 = 12.5% — a 1-in-8 shot, even though each leg felt like a coin flip.

Are parlays a good bet?

Usually not. Each leg carries the book's vig, and a parlay compounds it, so the house edge stacks with every leg. They're high-variance entertainment unless your legs are genuinely +EV or correlated.

Parlay Calculator — Odds, Payout & True Probability

Add your legs, set a stake, and get the combined odds, exact payout, and the real chance every leg hits. Works with American odds or Polymarket cents.

How the parlay calculator works

A parlay (or accumulator) is a single bet that only pays if every leg wins. The math is simple but unforgiving: convert each leg to a decimal multiplier, multiply them all together, and that product is your combined odds. Multiply by your stake to get the payout.

The core formula. Combined decimal odds = leg₁ × leg₂ × … × legₙ. True all-hit probability = (1 ÷ leg₁) × (1 ÷ leg₂) × … — i.e. each leg's implied chance multiplied together.

Worked example

Say you take three legs at +100 (2.00), -150 (1.67), and +108 (2.08). Combined decimal = 2.00 × 1.67 × 2.08 ≈ 6.95. A $50 stake returns 50 × 6.95 ≈ $347 ($297 profit). But the true chance all three land is (1/2.00)(1/1.67)(1/2.08) ≈ 14.4% — roughly 1-in-7.

Why parlays decay so fast

Every leg you add multiplies the payout and divides your probability. Three 50% coin-flips isn't a 50% bet — it's 0.5 × 0.5 × 0.5 = 12.5%, a 1-in-8 shot. Worse, each leg carries the sportsbook's vig, and a parlay compounds that edge, which is exactly why books push them so hard.

When a parlay is actually defensible

Two cases: correlated legs (outcomes that move together, like a team winning and going over the total), or legs that are each genuinely +EV on their own. If you're just stacking favorites for a bigger number, the math is working against you. Size it as entertainment.

Polymarket note. On Polymarket, a leg's price in cents is its implied probability (a 55¢ share = 55%). Switch this calculator to "Polymarket (¢)" mode to build a combo straight from share prices — the all-hit % is just the product of the cents.

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Parlay Calculator

Legs

How the parlay calculator works

Worked example

Why parlays decay so fast

When a parlay is actually defensible