Free betting calculators

Seven sports-betting math tools that run entirely in your browser. Price a parlay, convert odds, remove the vig, measure a book's hold, size a Kelly stake, check for an arb, and compute expected value.

No signup. No email. Nothing you type leaves your device; every calculation runs client-side.

Parlay Calculator

Use it to price a multi-leg bet: combine 2 to 12 legs into one price, payout, and combined implied probability.

/tools/parlay-calculator

Odds Converter

Use it when a price is in the wrong format: American, decimal, fractional, and implied probability, all in sync.

/tools/odds-converter

No-Vig / Devig Calculator

Use it to find the fair price: strips the bookmaker margin from a 2-way or 3-way market to get no-vig probabilities and odds.

/tools/no-vig-calculator

Hold Calculator

Use it to compare how expensive books are: enter every side of a market and see the hold percent, vig, and overround.

/tools/hold-calculator

Kelly Criterion Calculator

Use it to size a bet: turns your edge and the odds into an optimal stake fraction, with half and quarter Kelly for risk control.

/tools/kelly-calculator

Arbitrage Calculator

Use it when two books disagree: checks whether the prices lock in a guaranteed profit, with the exact stake split.

/tools/arbitrage-calculator

Expected Value (EV) Calculator

Use it to judge one bet: compares your price to a fair probability and shows the expected value in percent and dollars.

/tools/ev-calculator

These are the same calculations ParlayAPI runs at scale across 30+ sources: the /v1/ev and /v1/devig endpoints devig and price markets automatically so you do not have to. Free tier is 1,000 credits/month, no card. See pricing and the docs.