In this guide
An extra place calculator method: the inputs, formulas for place odds, lay stakes, qualifying loss and extra place profit, and two worked examples. 18+.
To work out any extra place bet you need six numbers: the win odds, the each-way fraction, the places paid by the bookmaker and by the exchange, the two lay odds and your exchange commission. From those, a few short formulas give the place odds, both lay stakes, the qualifying loss and what you make if the horse finishes in the extra place.
This page is a worked method you can follow with a phone calculator or a spreadsheet, not an interactive calculator. If you are new to the offer itself, start with extra place matched betting, step by step.
The inputs
- Win odds (W): the bookmaker's decimal odds for the horse to win. 7/1 is 8.0; add one to the fraction. See understanding betting odds if you need to convert.
- Each-way fraction (f): the share of the win odds the place half pays, usually 1/4 or 1/5. Checked against the terms of Paddy Power, Sky Bet, bet365, William Hill, Ladbrokes and Coral on 3 November 2026.
- Places paid: the bookmaker's places (for example 4) against the places in the exchange's place market (for example 3). The difference is the number of extra places.
- Lay win odds (Lw): the exchange price to lay the horse in the win market.
- Lay place odds (Lp): the exchange price to lay the horse in the place market that pays the standard places.
- Commission (c): the exchange's cut of net winnings, written as a decimal: 2% is 0.02.
- Stake (S): your stake per half. A £10 each-way bet means S = £10 and £20 in total.
Step by step: the formulas
- Step 1, place odds: P = 1 + (W − 1) × f. The fraction applies to the profit part of the odds only, so 8.0 at 1/5 gives 1 + 7 × 0.2 = 2.40, not 1.60.
- Step 2, win lay stake: S × W ÷ (Lw − c).
- Step 3, place lay stake: S × P ÷ (Lp − c). Use the place odds here, not the win odds.
- Step 4, liabilities: win lay stake × (Lw − 1) and place lay stake × (Lp − 1). Your exchange balance must cover both.
- Step 5, qualifying loss for each leg: S × ((L − c) − B × (1 − c)) ÷ (L − c), where B is the back odds of that leg (W or P) and L its lay odds. Add the two legs for the total qualifying loss.
- Step 6, extra place result: P × S − total qualifying loss. This is what you end with if the horse finishes in an extra place.
- Step 7, implied odds: P × S ÷ total qualifying loss. The break-even chance is 1 ÷ implied odds: the horse must finish in the extra places more often than that for the bet to have positive expected value.
- Step 8, optional rough chance: take 1 ÷ Lp (chance of placing on the exchange) minus 1 ÷ Lw (chance of winning), divide by the standard places minus one, and multiply by the number of extra places. Expected value is that chance × P × S − total qualifying loss.
Step 8 is a rough guide only. It gives every place below first an equal share, so it reads high for favourites and a little low for outsiders, and exchange prices carry a margin.
If both lays are matched at these stakes, winning, placing within the exchange's places and finishing unplaced all end at the same qualifying loss. That is the check that you have done the sums right.
Worked example 1: one extra place at 1/5
A bookmaker pays four places at 1/5; the exchange place market pays three. Inputs: W = 8.0, f = 1/5, Lw = 8.6, Lp = 2.50, c = 0.02, S = £10.
- Place odds: 1 + 7 × 1/5 = 2.40.
- Win lay stake: £10 × 8.0 ÷ 8.58 = £9.32. Liability: £9.32 × 7.6 = £70.86.
- Place lay stake: £10 × 2.40 ÷ 2.48 = £9.68. Liability: £9.68 × 1.50 = £14.52.
- Qualifying loss: £0.86 on the win leg plus £0.52 on the place leg = £1.38.
- Extra place result: 2.40 × £10 − £1.38 = +£22.62.
- Implied odds: £24.00 ÷ £1.38 = 17.4, a break-even chance of 5.7%.
- Rough chance: (1 ÷ 2.50 − 1 ÷ 8.6) ÷ 2 × 1 = (40.0% − 11.6%) ÷ 2 = 14.2%. Expected value: 0.142 × 2.40 × £10 − £1.38 = about +£2.03.
Outcomes: wins −£1.38; 2nd or 3rd −£1.38; 4th +£22.62; 5th or worse −£1.38. The rough chance is well above the 5.7% break-even, but the horse is near the front of the market, where this estimate reads high.
Worked example 2: a big handicap at 1/4
A bookmaker pays five places at 1/4 in a big handicap where the exchange place market pays four. Inputs: W = 15.0, f = 1/4, Lw = 16.0, Lp = 4.60, c = 0.02, S = £5.
- Place odds: 1 + 14 × 1/4 = 4.50.
- Win lay stake: £5 × 15.0 ÷ 15.98 = £4.69. Liability: £4.69 × 15 = £70.40.
- Place lay stake: £5 × 4.50 ÷ 4.58 = £4.91. Liability: £4.91 × 3.60 = £17.69.
- Qualifying loss: £0.40 on the win leg plus £0.19 on the place leg = £0.59.
- Extra place result: 4.50 × £5 − £0.59 = +£21.91.
- Implied odds: £22.50 ÷ £0.59 = 38.4, a break-even chance of 2.6%.
- Rough chance: (1 ÷ 4.60 − 1 ÷ 16.0) ÷ 3 × 1 = (21.7% − 6.3%) ÷ 3 = 5.2%. Expected value: 0.052 × 4.50 × £5 − £0.59 = about +£0.58.
Outcomes: wins −£0.59; 2nd to 4th −£0.59; 5th +£21.91; 6th or worse −£0.59. Note the liability: £88.09 at the exchange for a £10 bet at the bookmaker. Long-priced horses need a bigger exchange balance than their stake suggests.
Figures are rounded to the penny, so a leg can differ by a penny from the sum of its rounded parts.
Check your numbers
- The place odds are lower than the win odds and above 1. If not, the fraction was applied the wrong way.
- Commission is a decimal in every formula: 0.02, not 2.
- The win, placed and unplaced outcomes come out the same. If they differ by more than a penny or two, a lay stake is wrong.
- You are laying a place market that pays fewer places than the bookmaker. If both pay the same number, there is no extra place to win.
- Your exchange balance covers both liabilities, and both lays are fully matched, not part-matched.
- The bookmaker's places and fraction are the ones shown on your bet slip. Non-runners can change them, because the place terms go by the horses that actually run. Checked against the terms of William Hill, Ladbrokes and Coral on 3 November 2026. Check the bookmaker's current terms.
A spreadsheet version
Put W in B1, the fraction as a decimal (0.2 or 0.25) in B2, Lw in B3, Lp in B4, c in B5 and S in B6. Then:
- Place odds (B7): =1+(B1-1)*B2
- Win lay stake (B8): =B6*B1/(B3-B5)
- Place lay stake (B9): =B6*B7/(B4-B5)
- Qualifying loss (B10): =B6*((B3-B5)-B1*(1-B5))/(B3-B5)+B6*((B4-B5)-B7*(1-B5))/(B4-B5)
- Extra place result (B11): =B7*B6-B10
- Implied odds (B12): =B7*B6/B10
For more on each input, see understanding extra places and lay betting in matched betting.
Let the alerts do the arithmetic
Working this out by hand for one runner takes a few minutes. Doing it for every runner, at every bookmaker, in every extra place race, while prices move, is not practical. Our free list of today's extra place races shows which races carry an offer and the places each bookmaker pays, with the closest prices it found for the top five races from 09:00.
Innovision Labs Extra Places alerts run these sums for every runner and tell you when the back and lay prices meet your implied odds setting, by e-mail, web push or Discord. Members also get an extra place calculator in the dashboard for checking a bet before they place it. Alerts help you find close prices faster; they do not make a bet win, and you place every bet yourself.
Is there a free extra place calculator?
You can follow the method on this page with any calculator or the spreadsheet formulas above, at no cost. Our live matcher and dashboard calculator, which do the sums for you, are part of the Pro plan, which you can try free.
What is an each way lay calculator?
It works out the two lay stakes for an each-way bet: one for the win market and one for the place market. Steps 2 and 3 above are the whole of it; the only trap is using the place odds, not the win odds, for the place lay.
How do I calculate each way place odds?
Take one off the decimal win odds, multiply by the each-way fraction and add one back. 11.0 at 1/5 gives 1 + 10 × 0.2 = 3.00.
What commission should I use?
Use the rate your exchange charges you on net winnings, as a decimal. Rates differ between exchanges and can change: Betfair Exchange sets yours by your rewards package, and Smarkets by your account tier. Checked against the terms of Betfair Exchange and Smarkets on 3 November 2026. Check your exchange's current rate.
Safer betting
18+ only. Bookmakers and exchanges can change their offers and terms at any time. Always check the current terms on their site before you bet. Matched betting reduces risk but does not remove it: mistakes, price moves and voided bets can cause losses. Only bet what you can afford to lose. Please gamble responsibly. For free, confidential support visit GambleAware.org or call the National Gambling Helpline on 0808 8020 133. Our safer betting page.
Disclosure: this page contains no affiliate links. Innovision Labs sells the alerts mentioned on this page.
