Accumulator calculator

An accumulator, or acca, joins several selections into one bet. Every leg has to win, and in return the odds of all the legs are multiplied together. This calculator does the multiplication for you: type the decimal odds of each selection and your stake, and it shows the total odds, the potential return and the profit.

How to use the calculator

1. The calculator opens with two legs. Press Add selection for each extra leg of your slip.
2. Type each leg's decimal odds, as shown in your betting app.
3. Enter your stake in any currency: shillings, naira, cedis, kwacha.
4. Read the total odds, the return and the profit underneath. Remove takes a leg off if you change your mind.

Nothing you type is sent anywhere; the sums are worked out on your phone.

The maths behind an acca

Total odds = odds of leg 1 × odds of leg 2 × odds of leg 3 …

Return = stake × total odds. Profit = return − stake.

Three legs at 1.50, 1.80 and 2.10 give total odds of 5.67. A stake of 100 returns 567, a profit of 467. If any one leg loses, the whole slip loses and the return is zero.

If a match is postponed or a leg is voided, most bookmakers count that leg at odds of 1.00 and settle the rest. Enter the remaining legs to see the new figure.

The chance that the slip comes in

Probabilities multiply too. If the three legs above have chances of 70%, 58% and 50%, the slip lands 0.70 × 0.58 × 0.50 = 20.3% of the time, about once in five. Its fair odds are 1 ÷ 0.203, about 4.93. Here the offered 5.67 is above that figure, so on these numbers the slip pays more than its risk. Most slips are not like that.

Each extra leg cuts the chance sharply. Five legs at 80% each land together only about 33% of the time, even though every single one looks strong on its own.

Why bookmaker margins grow in an acca

Every price includes a margin for the bookmaker. On a single, that might mean getting back around 95% of a fair payout. In an accumulator the shortfalls multiply. Say three legs each have a true chance of 53%, so a fair price of about 1.89, and the bookmaker pays 1.80 on each. The acca pays 1.80 × 1.80 × 1.80 = 5.83, but the fair price for a 14.9% chance is about 6.72. You are getting roughly 87% of a fair payout instead of 95%. The more legs, the bigger the gap.

Fair odds and true odds

Fair odds are the price with no margin: fair odds = 1 ÷ probability.

Probability	Fair odds
80%	1.25
70%	1.43
60%	1.67
50%	2.00
31%	3.23
20%	5.00

Every tip on PitchMaths shows its fair odds next to the probability, so you can compare them with your app's price before adding a leg.

Taking the margin out of 1X2 odds

To turn a bookmaker's 1X2 prices into true odds, convert each price to an implied chance (1 ÷ odds), add them up, and divide each by the total. Prices of 2.10, 3.30 and 3.60 give 47.6% + 30.3% + 27.8% = 105.7%. The extra 5.7% is the margin. Dividing each by 1.057 gives 45.1% home, 28.7% draw and 26.3% away, which are fair odds of 2.22, 3.49 and 3.81. Our model blends its own match result chances half and half with numbers like these where odds are in our data; how our predictions are made explains the blend.

System bets: Trixie, Yankee and others

A system bet covers every combination of a set of selections, so you can still win something when one leg loses. The cost is more bets for the same stake per line.

• 2 from 3: three doubles.
• Trixie: three selections, four bets: three doubles and a treble.
• Patent: three selections, seven bets: three singles, three doubles and a treble.
• Yankee: four selections, eleven bets: six doubles, four trebles and a fourfold.
• Lucky 15: a Yankee plus the four singles, fifteen bets.

A Yankee at 10 per bet costs 110 in total. To find its return, enter each combination of winning legs in the calculator and add the results.

Other odds formats

The calculator uses decimal odds. To convert fractional odds, divide and add 1: 5/2 becomes 3.50, 1/2 becomes 1.50. For American odds, +150 becomes 2.50 (150 ÷ 100 + 1) and −200 becomes 1.50 (100 ÷ 200 + 1).

Building a slip with our tips

Legs rated high are the usual building blocks: see double chance predictions and the strongest tips on today's predictions. The weekend predictions page has a ready-made slip built to reach odds of about 5 from legs rated 70% or more, which at near-fair prices should land about one time in five. If you want a draw to refund a leg rather than lose it, draw no bet is the market to read about, and the safer goal lines are explained in over and under goals explained.

You must be 18+ to bet. A bigger total is a smaller chance, not a better bet. Any bet can lose; stake only what you can afford.