What Is a Back Bet?
A back bet is a bet that a specific outcome will happen. It's the same as what you'd place at a high street bookmaker or betting app: you pick something, you stake money on it, and if your selection wins you profit. If it doesn't, you lose your stake.
On Betfair Exchange, the mechanics are the same but the context is different. Your back bet isn't being taken by Betfair — it's being matched against another user who has placed a lay bet on the same selection at the same price. That user believes the outcome will NOT happen and is willing to act as the bookmaker.
Betfair's matching engine finds these two orders, brings them together, and holds both parties' funds in escrow until the market is settled. Betfair itself takes a small commission from the winner.
You back Liverpool at 2.20 for £100.
If Liverpool win: you receive (2.20 − 1) × £100 = £120 profit. Plus your stake returned = £220 total. Commission deducted from profit.
If Liverpool don't win: you lose your £100 stake. No commission charged on losing bets.
How Decimal Odds Work
Betfair Exchange displays all odds in decimal format. This is different from the fractional odds you may be used to from traditional UK bookmakers (like 2/1 or 11/4). Decimal odds represent your total return per £1 staked, including your original stake.
So decimal odds of 3.00 means: for every £1 you back, you get £3 back total if you win — that's £2 profit plus your £1 stake returned. To calculate just the profit: (odds − 1) × stake.
| Fractional | Decimal | Implied Probability | £100 stake profit |
|---|---|---|---|
| Evens (1/1) | 2.00 | 50.0% | £100.00 |
| 6/4 | 2.50 | 40.0% | £150.00 |
| 2/1 | 3.00 | 33.3% | £200.00 |
| 5/2 | 3.50 | 28.6% | £250.00 |
| 4/1 | 5.00 | 20.0% | £400.00 |
| 10/1 | 11.00 | 9.1% | £1,000.00 |
| 33/1 | 34.00 | 2.9% | £3,300.00 |
To convert fractional odds to decimal: divide the numerator by the denominator, then add 1. Example: 7/2 = (7 ÷ 2) + 1 = 4.50. To convert decimal to fractional: subtract 1 and simplify. Example: 4.50 − 1 = 3.50 = 7/2.
Implied probability is useful for assessing value. Divide 1 by the decimal odds: 1 ÷ 2.50 = 40%. If you think a horse has a greater than 40% chance of winning and the market is offering 2.50, that's a value back bet. See our trading calculator for instant conversion between formats.
Calculating Your Returns
The formula for a back bet return is simple:
- Gross profit: (Odds − 1) × Stake
- Total return: Odds × Stake
- Net profit after commission: Gross profit × (1 − commission rate)
Back a horse at 6.00 for £50 in a UK horse racing market (2% commission).
Gross profit if it wins: (6.00 − 1) × £50 = £250.
Commission: £250 × 2% = £5.
Net profit: £245. Total received: £295 (profit + stake returned).
If it loses: you lose £50. No commission.
Always calculate P&L using net figures. Many beginners track gross winnings and are confused when their balance doesn't match expectations. Commission at 5% on a £200 win is £10 — significant at scale.
How to Place a Back Bet: Step by Step
On the standard Betfair website:
Go to betfair.com, select Exchange (not Sportsbook), choose your sport, and find the event. Click the market you want — e.g. "Manchester City v Arsenal — Match Odds".
The blue column shows current back prices for each selection. Click the price next to the selection you want to back. A bet slip opens on the right side of the screen with your selected price pre-filled.
Type your stake amount in the stake field. The bet slip will show your potential profit (gross, before commission) automatically.
The price in the bet slip defaults to the best available back price. You can change it to request a better (higher) price — but your bet may not be matched immediately, or at all, if no one is willing to lay at that price.
Review the details and confirm. Your bet will be placed and either matched immediately or sit as unmatched in the queue.
For active trading — pre-race horse racing, in-play markets — the standard Betfair website is too slow and limited. Third-party software like Bet Angel or Geeks Toy provides a trading ladder with one-click back/lay, instant price refresh, and proper P&L tracking. See best trading software 2026.
Matched vs Unmatched Bets
When you place a back bet on the Exchange, Betfair tries to match it immediately against an existing lay order at the same price. If a match is found, your bet is matched — it's live and you cannot cancel it.
If no lay order exists at your requested price, your bet sits as unmatched — it's in the queue but not yet active. An unmatched bet:
- Can be cancelled at any time before matching
- Will be matched automatically if someone comes in with a lay at your price
- Can be partially matched — some of your stake matched, some still unmatched
- At race start, will either match at BSP or be cancelled depending on your settings
Unmatched bets are shown in your account as "Unmatched". Always check whether your bet has actually matched before the market turns in-play. An unmatched bet left over at race start behaves differently from what many beginners expect — see our BSP guide for the full explanation.
Why Exchange Odds Are Better
Traditional bookmakers build a profit margin (overround) into every set of odds they offer. For a typical Premier League match, a bookmaker's book might total 108–112% implied probability across the three outcomes (home win, draw, away win). That extra 8–12% above 100% is their margin — effectively a hidden tax on every bet.
The Exchange has no bookmaker margin. The only cost is commission on net winnings. This means the sum of implied probabilities on the Exchange is typically 100–102% — near-perfect efficiency. The result: Exchange prices are routinely better than bookmaker prices on the same market, often by 5–15% on shorter-priced selections.
Chelsea vs Tottenham. Chelsea to win:
Bookmaker A: 1.80 (implies 55.6% probability)
Betfair Exchange: 1.95 (implies 51.3% probability)
On a £200 back bet, that's a difference of £30 in profit if Chelsea win. Over hundreds of bets, this gap is enormous.
The Exchange advantage is most pronounced on short-priced selections (under 3.00). On longshots (10.00+), bookmaker and Exchange prices are often similar because the margin is a smaller absolute figure. See Exchange vs Sportsbook for a full comparison.
Using Back Bets in Trading
For traders, backing is just one half of the equation. You back a selection expecting the odds to shorten, then lay the same selection at a lower price to lock in profit regardless of the result. The back bet opens the position; the lay bet closes it.
Open position: Back Favourite in the 3:45 at Cheltenham at 3.50 for £100. Potential profit: £250. Risk: £100.
20 minutes later: The horse shortens to 2.80 (good news in the paddock, a market mover has backed it heavily).
Close position: Lay at 2.80 for £125 stake (the calculated hedge amount).
Result if horse wins: +£250 (back) − £225 (lay liability) = +£25 profit.
Result if horse loses: −£100 (back) + £125 (lay stake collected) = +£25 profit.
Guaranteed £25 profit regardless of result — before commission (2% = £5, net profit £20).
This is swing trading — back first, lay later. For full strategy walkthroughs, see Swing Trading on Betfair and What Is Betfair Trading?. To calculate the correct lay stake for any back bet, use our trading calculator.
Common Mistakes When Back Betting
- Not accounting for commission: Gross profit and net profit are different numbers. Always use net in your P&L tracking.
- Requesting a price that won't get matched: If you ask for 4.50 and the market is at 3.80, your bet sits unmatched. Check the available prices before placing.
- Backing at the last second and missing the price: In liquid pre-race markets, prices move every few seconds in the final minutes. The price you click may be gone by the time your order reaches the engine. Trading software with direct API access significantly reduces this delay.
- Ignoring liquidity: In a thin market (under £50K matched), your back bet may move the price against you or sit unmatched entirely. Stick to high-liquidity markets as a beginner.
- Over-staking relative to bankroll: No single back bet should risk more than 2–5% of your total trading bankroll. See bankroll management.
Back betting involves real financial risk. You can lose your entire stake on any bet. Never back with money you cannot afford to lose. Set deposit limits before you start. Understand the commission impact on your P&L before placing real money.
Next Steps
Back betting is the foundation. Once you're comfortable with how returns work and how to get matched, the next logical step is understanding lay betting — the other side of every Exchange transaction and the tool that opens up trading strategies unavailable at any bookmaker.
After that, What Is Betfair Trading? explains how combining back and lay bets creates a position you can profit from regardless of the result.
No Betfair account yet? Open one in 15 minutes and start with the Exchange tutorial markets (practice mode) before using real money.
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