Calculating margin on an NRL head-to-head market

Use one complete head-to-head quote

Take the two decimal prices for the same NRL head-to-head market from one bookmaker at one capture time. Divide one by each price, add the fractions and subtract one. The result is the market's displayed overround. It is a pricing measure, not a forecast of who will win.

Do not mix a favourite price from Book A with an underdog price from Book B and call the result Book A's margin. A cross-book pair is useful for shopping one selection, but it is a different calculation.

Why a smaller margin is not the whole answer

A bookmaker with a lower two-way overround may still offer a worse price on the specific team you want. Compare that team's identical head-to-head selection directly across books. Market margin describes the pair of quotes; your payout depends on your selected quote.

If one side is missing or suspended, do not calculate a complete margin from the remaining price. Confirm the official NRL fixture and bookmaker settlement period first.

Record the snapshot

Odds change. A reproducible comparison names the fixture, bookmaker, both prices and capture time. It can then be compared with another snapshot without confusing a line bet, an old quote or a different match.

• Use both teams from one bookmaker's head-to-head market.
• Calculate before rounding.
• Separate bookmaker margin from the best price for one selection.