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Betting Odds Converter

Convert between American, decimal, fractional odds and implied probability, with the bookmaker's vig.

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Open Betting Odds Converter and you get an answer straight away, with no account to create. Its place is under Random generators; Bingo Card Generator and Coin Flipper answer the questions closest to this one.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Betting Odds Converter do?

Convert between American, decimal, fractional odds and implied probability, with the bookmaker's vig.

When would I actually use this?

Producing something plausible on demand: a name for a pet or a domain, a sentence to test a layout with, a cocktail for what is already in the cupboard, a character sheet to start a campaign — and the throwaway identities a form needs before it can be tested at all.

What is the most common mistake?

Letting a generated identity out of the test environment. A fake address, a valid-looking card number and a plausible name are built to pass a form's checks, which is exactly what makes them dangerous once a real record is created from them — and a generated domain or pet name still has to be checked for a trademark nobody here can see.

What else is filed next to it?

Bingo Card Generator, Coin Flipper and List Randomizer share its section. They are not variants of it — being filed together is not the same as being alike — but that is where to look if this turned out not to be the tool you wanted.

Where do the figures come from?

Randomness comes from the browser's cryptographic source, so an identifier is safe to use as a key. The card numbers satisfy the Luhn check and the issuer prefixes precisely so a payment form will accept them in test mode; no account stands behind any of them.

Further reading

All guides →
ExplainerThe Sum of the Implied Probabilities Is Never One HundredTwo sides both priced at -110 imply 52.4 % each. That adds to 104.8 %, and the 4.8 points that should not exist are the margin — visible the moment you convert the odds.ExplainerThe Expected Value Is a Number That Never HappensOutcomes of 10, 20 and −5 with probabilities 0.5, 0.3 and 0.2 give an expected value of 10. Shift the probabilities slightly and it becomes 10.5 — a result none of the three outcomes can produce.ExplainerThree Dice Cluster, and One Die Does Not3d6 and 1d20 have almost the same average and nothing else in common. Against a target of 12 the three dice are better, against 18 they are five times worse — and the calculator gives the exact figures rather than a simulation.How-toHow to Pick a Name at Random — Without Anyone Doubting the ResultA fair draw needs more than a random number: equal probability, no reuse of a biased method, and a result someone else can check. Here is how to run one.ExplainerTest Card Numbers: What the Luhn Algorithm Is Actually For, and What It Cannot Tell YouLuhn is a checksum for catching typos, patented in 1960, and that is its entire job. A number that passes it tells you nothing about any account. For testing a payment integration you need your processor's published numbers, not a generated one.GuideTournament Brackets: Byes, Seeds, and Why the Numbers Must Be Powers of TwoA knockout bracket halves its field every round, so it only closes on a power of two. The bye count, the round count, the seed order and the total number of matches all follow from that one fact — and each is a one-line derivation.