Flat units or a percentage of bankroll: the same run of results both ways

With flat staking every bet is the same amount, and with percentage staking every bet is a share of the current bankroll. Over 100 even-money bets with 40 wins on a 1,000 start, a flat 20 ends at 600 and a 2% stake ends at 657. With 50 wins, flat ends at 1,000 and percentage at 980.

The unit size calculator sets the unit under either method from your bankroll and a percentage.

What each method does

Flat. Fix the unit at the start, 2% of 1,000 is 20, and keep staking 20 until you decide to change it. A loss costs 20 whether the bankroll is 1,000 or 400.

Percentage. Recompute 2% of the current bankroll before every bet. After a loss of 20 the next stake is 19.60, and after a win it is 20.40. Stakes shrink in drawdowns and grow in good runs.

Ten bets at even money

One hundred bets at even money

The gap grows because the percentage method compounds. At 2% and even money, one win and one loss in either order multiply the bankroll by 1.02 × 0.98 = 0.9996. Staking by percentage loses a sliver on every pair, a small drag that comes from compounding.

• 50 wins, 50 losses. Flat: 1,000. Percentage: 0.9996^50 × 1,000 = 980.19.
• 40 wins, 60 losses. Flat: 20 net losses × 20 = -400, ending at 600. Percentage: 1.02^40 × 0.98^60 = 0.657, ending at 657.
• 60 wins, 40 losses. Flat: 20 net wins × 20 = +400, ending at 1,400. Percentage: 1.02^60 × 0.98^40 = 1.462, ending at 1462.

The difference that matters in a bad run

Flat staking can lose the whole bankroll: after 50 net losses at 20 a bet from a 1,000 start, nothing is left. Percentage staking never reaches zero, because every stake is a share of what remains. After 30 wins and 90 losses in 120 bets, a 2% stake leaves 1.02^30 × 0.98^90 = 0.294 of the start, about 294, still staking small amounts, while flat staking passed zero at 50 net losses. That protection has a cost: the bankroll recovers more slowly, since stakes are small exactly when it needs a big recovery. A bankroll down 50% needs a 100% gain, and with stakes cut in half the climb back takes longer.

Which to use

• Flat is easy to keep, easy to record and easy to compare across weeks, and it is what most people mean by "units".
• Percentage adjusts risk to the bankroll automatically and cannot reach zero, and it makes your record harder to read because the unit keeps changing.
• A common middle route is flat units that are reset on a schedule, such as monthly, to the chosen percentage of the bankroll at that date. The reasons are in the article on units and comparable records.

Set the unit. The unit size calculator gives the current unit for any bankroll and percentage so you can reset it on whatever schedule you pick.