How to work out bet builder odds
Why the legs multiplied is the wrong number, and how to get the right one in under a minute.
Quick answer
You can’t work out a bet builder by multiplying the odds, because legs in the same match are linked. Enter each leg’s price into a bet builder calculator: it strips the margin from each leg, allows for how the legs move together, and gives a fair combined price to compare with your quote.
Key facts
- Legs in the same match are correlated: a team winning makes goals more likely, so the legs don’t combine like an accumulator across different matches.
- Every leg’s price includes a bookmaker margin, and those margins stack as you add legs.
- Example: Home Win at 1.80 and Over 2.5 Goals at 2.10 multiply to 3.78, but the model’s fair price is 3.22.
- The fair price is an estimate from a model, not a prediction. Use it to compare quotes, not as a tip.
Work out a bet builder in 5 steps
Open the bet builder calculator
Go to the BetCalc365 bet builder calculator. It works for football bet builders with up to ten legs.
Add each leg and its odds
Pick the market for each leg (for example Home Win, Over 2.5 Goals, a player to be carded) and type the odds shown for that leg on its own. Decimal, fractional and American odds all work.
Add the match odds if you have them
Enter the home, draw and away prices and the over/under 2.5 price. For goals-based legs this lets the calculator fit the match itself rather than use general rules, which makes the fair price more accurate.
Enter the price you are quoted
Type the bet builder price your bookmaker shows for the whole combination. This unlocks the comparison.
Read the result
The calculator shows three numbers: the legs multiplied, the fair odds from the model, and your quote. The expected value figure tells you how the quote compares with the fair price.
Worked example: Home Win + Over 2.5 Goals
The two legs are priced 1.80 and 2.10 on their own. These figures come straight from the calculator’s engine.
| What | Odds | What it means |
|---|---|---|
| Legs multiplied | 3.78 | The price if the two legs had nothing to do with each other |
| Fair odds (model) | 3.22 | After removing an average 5.8% margin per leg and allowing for the link between the legs |
| If you are quoted 3.50 | +8.6% | Expected value against the fair price: the quote is longer than fair |
| If you are quoted 2.90 | −10.0% | Expected value against the fair price: the quote is shorter than fair |
Expected value is the average result per £1 staked if the model’s fair price were exactly right. It is a comparison tool, and the model is an estimate.
Why multiplying the legs gives the wrong answer
Multiplying odds assumes each leg is independent, which is true for an accumulator across four different matches and false inside one match. If the home side wins, the game has usually had goals, so "home win" and "over 2.5 goals" tend to land together. That makes the combination more likely than the legs multiplied suggests, and the fair price shorter.
The second effect is margin. Each leg’s price has the bookmaker’s margin built in, and player markets such as shots and cards carry more than the main match markets. The calculator removes the margin from each leg before combining them, so you see the two effects separately.
If margin is new to you, the UK guide to bookmaker margin and overround explains where it comes from and how to measure it in any market.
Common questions
Can I just multiply the odds for a bet builder?
Why is my bet builder price lower than the legs multiplied?
How accurate are the fair odds?
Does it work for player shots and cards builders?
How many legs can I add?
Related tools and guides
- Bet builder calculator, fair odds and expected value for any same-game combination.
- How we price a bet builder, the method behind the calculator, in detail.
- Football betting, football tools and guides in one place.
Worked examples on this page are produced by the same calculation engine as the calculators. 18+. Bet responsibly: help and tools.