The calculator compares the actual race time against a standard par time for the given distance on Good going, then adjusts for the official going description.

1. Par time: Each distance has a benchmark time on Good ground, derived from typical course standards.

2. Going allowance: Faster ground (Firm) reduces the par time; slower ground (Heavy) increases it. The allowance is applied per furlong.

3. Speed figure: The difference between the adjusted par and the actual time, converted to lengths using a distance-specific lengths-per-second value, then added to a base of 80.

Note: Speed figures are an approximation and do not account for race tactics, weight carried, draw bias, or track configuration. They are most useful for comparing performances across similar distances and going conditions.