Calculators
Bet journal, bankroll and Kelly calculator in your browser
Log each bet and see your profit or loss, ROI and longest losing run. The Kelly fraction is shown as a teaching number. No sign-up: data stays in your browser.
Set a monthly limit: the most you are fine to stake in a month. Only you see it.
October 2026: $0.00 staked so far.
No bets yet. Add one above – it stays in this browser only.
Kelly fraction – a teaching number
This is what the formula gives if your 52.0% is right. The price says 47.6% before the margin.
- Kelly assumes your chance is correct. Nobody knows it exactly.
- Overestimate the chance and Kelly overbets: the stake grows faster than the edge you really have.
- Even with a real edge, losing runs are normal; half or quarter Kelly swings less.
Saved only in this browser on this device: no account, nothing sent to us. Clearing site data deletes it – download a CSV to keep a copy.
How the numbers work
Won: stake × (odds − 1). Lost: minus the stake. Push and void: the stake comes back, net 0. Cash out: the amount you got minus the stake.
Return on money staked = net result ÷ money staked on settled bets. The monthly limit counts every bet placed that month, open or settled.
Keep a bet journal
- Write the dateLog the day you placed the bet. Entering bets late makes losing runs easy to miss.
- Name the betGame, market and side, for example the puck line or the 60-minute line. Be specific so you can review it later.
- Record the priceCopy the exact odds you got. The margin calculator shows the operator's margin across all outcomes of the market.
- Enter the stakeThe amount you risked. Log every bet, small ones too, or the totals will be wrong.
- Log the resultWin, loss or push, and the amount returned. The journal adds up profit/loss, ROI and your longest losing run.
What the journal shows
| Number | What it means |
|---|---|
| Profit/loss | Total returned minus total staked |
| ROI | Profit divided by total staked |
| Longest losing run | Most losses in a row |
| Kelly fraction | Formula output, not a stake to place |
Kelly fraction in one line
f = (p × d − 1) ÷ (d − 1); p = your win probability, d = decimal odds
Example: (0.42 × 2.50 − 1) ÷ (2.50 − 1) = 3.3% of the bankroll, and only if your 42% estimate is correct.
Kelly is a teaching number
Full Kelly
3.3%Share of bankroll from the example. Swings are large, and an overestimated probability makes the number too high.
Quarter Kelly
0.83%A quarter of full Kelly. Smaller swings, but it still depends on your probability guess and can still lose.
Negative edge
−$1.00Expected value of a $20.00 bet at the formula example's odds if the true chance is 38%. Kelly below zero means the formula finds no edge.
Flat stake vs percentage stake
Flat stake
- Same amount on every bet, for example one unit
- Easy to log and compare results
- Stake does not shrink after losses
Percentage of bankroll
- Stake is a fixed share of the current bankroll
- Stake drops after losses and rises after wins
- Needs recounting before each bet
- Kelly is one percentage method; full size swings most
Questions
What is a Kelly calculator?
It applies the Kelly criterion: a formula that turns your win probability and the decimal odds into a share of bankroll. It is not a recommended stake. A wrong probability gives a wrong number.
Is full Kelly too risky for sports betting?
Full Kelly causes large swings and assumes your probability is exact. Some people look at a fraction, such as quarter Kelly (0.83% in the example), but any stake can lose.
Where is my bet journal saved?
Only in your browser on this device. There is no account and no sign-up. Clearing site data deletes it, and another browser will not show it, so write down any totals you want to keep.
What is a unit in betting?
A unit is a fixed stake you choose yourself. Logging bets in units makes results easier to compare over time, whatever the bankroll size.
Are betting winnings taxable in Canada?
See are gambling winnings taxable in Canada for details. A journal helps you know your real totals; this page is not tax or legal advice.