Race Time Calculator
Choose the original race-time calculation or cutoff-buffer mode. Both use arithmetic only and do not predict performance.
A QUICK WALKTHROUGH
How to use this tool
- For race time, enter distance, distance unit, pace minutes and seconds, and pace unit.
- For cutoff buffer, enter distance, cutoff as decimal minutes, and planned pace as decimal min/km; the new mode does not accept h:mm notation.
- Optionally add 1–20 slower-pace scenarios in seconds per kilometre, then calculate and copy or download the result.
Original race-time mode and unit conversions
The original distance × pace mode remains available. Distance may be kilometres or miles; pace may be minutes per kilometre or mile. Mile-to-kilometre distance uses 1 mile = 1.609344 km, and pace per mile is converted back by the same factor. Time is calculated before display formatting.
Cutoff-buffer mode
Enter cutoff time as decimal minutes (for example 390), and planned pace as decimal minutes per kilometre (for example 8.5). Finish minutes = distance in km × planned min/km; buffer = cutoff − finish; buffer percentage = buffer ÷ cutoff × 100; cutoff pace = cutoff ÷ distance; pace margin = cutoff pace − planned pace. User-entered slowdown seconds/km are converted to minutes/km only for each scenario.
Scope and precision
Scenario tables show user-entered slower seconds per kilometre and the resulting finish and signed buffer. Negative buffer means a scenario is over cutoff. Formatting to h:mm:ss or min/km is presentation only; arithmetic uses unrounded floating-point values, and the TXT report retains raw inputs and numeric outputs. This does not model checkpoints, terrain, aid stations, fatigue, fitness, or likely performance.
GOOD TO KNOW
Common questions
How do I enter a cutoff time in the new mode?
Use decimal minutes, such as 390 for six and a half hours. The cutoff field is not an h:mm clock field.
Can I enter planned pace as min/mile in cutoff mode?
The cutoff-mode pace input is decimal min/km. The distance may still use the existing km or mile selector and is converted to kilometres for the calculation.
Does a positive buffer guarantee that I will beat the cutoff?
No. It is only a constant-pace calculation against the single entered cutoff and does not account for checkpoints or race conditions.