thewizardofodds.com publishes calculators for UK betting arithmetic: free bet extraction, qualifying bets and odds conversion. Everything runs in your browser. There is no account, nothing is stored, and nothing is sent anywhere.
What this is not
This is not The Wizard of Odds. That is Michael Shackleford's gambling-mathematics site, which covers casino game analysis — house edge, blackjack strategy, video poker returns — and it is at wizardofodds.com. This site has no connection to it, is not affiliated with it, and does not republish any of its material. If that is what you were looking for, go there.
This is not an affiliate site. It lists no bookmakers, ranks nothing, recommends nothing and carries no offers. It has no commercial relationship with any operator.
This is not advice. The calculators do arithmetic on figures you type in. They have no view on whether a bet is a good idea, and they cannot see the terms attached to any particular offer.
On the arithmetic
Every formula used here is derived on the page that uses it, and the calculators print their working so a result can be checked by hand. If something is wrong, it should be possible to see exactly where — and worth telling us about.
Betting has a negative expected value by design. The margin described on the odds converter page is not an accident; it is the business model. No amount of arithmetic changes that.