// Guide

Betting Calculators: Free Tools for Odds, Parlays, Hedging and EV

Nine free betting calculators for converting odds, pricing parlays, hedging, arbitrage, Kelly staking, expected value and UK each-way and Lucky 15 bets.

By Drone Bet Team Updated October 22, 2026 3 min read

Every serious bettor runs the same handful of sums. They work out what a price implies, what a parlay pays, how much to stake and whether the bet is worth making. Our free betting calculators do that math in seconds, with no sign-up and no sportsbook links attached to the answer.

Each tool has its own page with the formula, a worked example and guidance on when to use it.

Odds and probability calculators

Odds converter

Switch between American (+150), decimal (2.50) and fractional (3/2) odds instantly, with the implied probability alongside. Useful when you compare US sportsbooks with UK bookmakers, exchanges or prediction markets.

Implied probability calculator

Turn any price into the chance the market is assigning, then strip out the sportsbook’s margin to find the fair, no-vig probability. This is the single most useful number in betting.

Bet builders and payout calculators

Parlay calculator

Enter your legs and see the combined price, total payout and the probability the parlay lands. It also shows how quickly the book’s margin compounds with every leg.

Each-way calculator (UK)

Work out the win and place returns on an each-way bet at any place terms, from 1/4 odds two places to enhanced extra-place offers. Built for UK horse racing and golf.

Lucky 15 calculator (UK)

Price all 15 bets in a Lucky 15 so you know the return from one winner to four.

Staking and risk calculators

Hedge calculator

Sitting on a futures ticket or the last leg of a parlay? Calculate the hedge that locks in equal profit, or the smaller one that simply gets your stake back.

Kelly criterion calculator

Enter your bankroll, the odds and your estimated win probability to get the stake the Kelly formula recommends. Most bettors then stake a half or a quarter of it for a safer ride.

Edge-finding calculators

Expected value calculator

Compare your probability with the sportsbook’s price to see what a bet is worth on average, in dollars and as a percentage of stake. Positive EV is the whole game.

Arbitrage calculator

When two books disagree enough, backing every outcome guarantees a profit. This tool checks whether a surebet exists and splits your stake so you win the same amount whatever happens.

Which betting calculator do you need?

Question	Calculator
What does +250 mean in decimal?	Odds converter
What chance is the sportsbook giving this team?	Implied probability
What will my four-leg parlay pay?	Parlay calculator
Should I bet the other side to lock in profit?	Hedge calculator
Is this a guaranteed profit across two books?	Arbitrage calculator
How much should I stake?	Kelly criterion calculator
Is this bet worth making?	Expected value calculator
What does my each-way bet return if it places?	Each-way calculator
What do I win if two of my four horses win?	Lucky 15 calculator

Why the math matters more than the picks

Most bettors spend their energy on who will win. Professionals spend it on price. A standard -110 line implies a 52.38% chance on each side, so the sportsbook’s two prices add up to more than 100%. That gap is the house edge, and it applies to every bet you make. You do not beat it by picking more winners. You beat it by betting only when your probability is higher than the price implies, and by staking sensibly when it is.

That is exactly what the AI betting tools on the market automate. Our guide to the best AI sports betting tools covers paid options such as OddsJam, Outlier and Rithmm. These calculators give you the same core math for free.

Using these tools with prediction markets

Event contracts on Kalshi, Polymarket and similar platforms are priced in cents, and the price is the implied probability, so 35 cents means 35%. Convert it to odds and every calculator here works the same way. Just subtract trading fees from the payout. See our prediction markets hub for how each platform charges.

21+ only for US sports betting. Calculators are for information; check the payout on your bet slip before you confirm. Gambling problem? Call 1-800-GAMBLER.

FAQ

What is the most useful betting calculator?

The implied probability calculator, because it turns any price into the chance the sportsbook is assigning. Once you think in probabilities, every other tool, from expected value to Kelly staking, makes more sense.

Are betting calculators accurate?

The math is exact, but the output is only as good as the inputs. A Kelly or expected value result depends on your own probability estimate, and sportsbooks may round payouts or apply limits that change the actual return.

Do sportsbooks show the same payout as a parlay calculator?

Usually, though some books round decimal odds or adjust correlated legs differently. Always check the potential payout on the bet slip before you confirm.

Can I use these calculators for prediction markets?

Yes. A contract priced at 40 cents is a 40% implied probability, equivalent to +150 or 2.50 decimal before fees. The odds converter, expected value and Kelly calculators all work once you convert the price.