What does this result mean?
Larger bets allow the defender to fold a greater share of the range in this model. MDF is not a universal instruction to call.
Minimum defence frequency calculator
Updated October 2026 · by Tom Howcroft
Calculate the river defence and bluff ratios for a bet size. Free, no account. See the formula, assumptions and editable inputs.
£100
£50
66.7%
Minimum defence
33.3%
Break-even folds for zero-equity bluff
33.3
Bluffs per 100 value bets
Bluff share of betting range
Example
The example inputs below are hypothetical. Change them to inspect your own study scenario. Compare bet sizes against one unchanged pot before applying any reads about the bettor's range.
Estimates for study and planning only, not a profit promise. Overshove tracks your real sample so these inputs come from your own data.
How to use the answer responsibly
Treat the calculator as a planning tool, not a verdict on one session. A live poker input is usually an estimate: your win rate is noisy, your standard deviation changes by game type, and your future volume rarely matches the clean number you type into a form. The useful habit is to save the assumptions beside the result so you know what would need to change before the decision changes.
If the result pushes against what you wanted to do, do not smooth the inputs until the answer feels nicer. Make the conservative version first, using a lower win rate, a higher swing rate or fewer weekly hours. Then run the optimistic version. The space between those answers is the real decision area: where a shot needs a stop rule, where a move up needs more buy-ins, or where a good-looking hourly still needs a bigger sample.
Overshove calculators become more useful when the inputs come from your own logged sessions. Rake, tips, travel, hours, stake mix and session length all change the number. A generic benchmark can teach the shape of the problem, but a clean personal log gives the number you should actually act on.
Questions
What formula does this tool use?
MDF = pot / (pot + bet). The indifference bluff-to-value ratio = bet / (pot + bet); bluff share = bet / (pot + 2 × bet). Assumes a polar river bet, bluff catchers, no rake and no later betting.
Is this tool free and does it require an account?
It runs in your browser for free with no account. The result is a study calculation under the stated assumptions, not a recommendation to play or a promise of winnings.