About Runner's Math

Runner's Math started because I wanted better splits for Boston. The generic "divide your goal time by 26.2" approach ignores the hills, the weather, and the fact that mile 22 doesn't feel like mile 2. So I built something that actually models those things. It's free, it works on your phone, and you don't need an account to use most of it.

What We Offer

• ▸Pace calculator with VDOT training zones, race predictions, and effort equivalency
• ▸Course-specific race plans for 35+ real courses with mile-by-mile pacing
• ▸Weather-adjusted pacing using race-day forecasts
• ▸Printable pace bands you can wear on your wrist during the race
• ▸Shareable race plans so friends and spectators can follow along

How Our Pace Model Works

Most pace calculators give you even splits and call it a day. Ours models what actually happens out there:

• ▸Elevation grade adjustments : uphills slow you down, moderate downhills help, steep downhills hurt. Based on published cost-of-running research
• ▸Cumulative fatigue modeling : your pace drifts as glycogen runs out, and the model knows when
• ▸Quad damage from steep descents : long descents trash your quads and it compounds. Ask anyone who's done Boston
• ▸Heat stress from weather : a 70°F dew point costs you more than most people realize
• ▸First-mile congestion : crowded corral, slow first mile. We bake that in
• ▸Aid station time : brief stops add up, especially in ultras

Data Sources

• ▸GPX course data — sourced from official race organizations and verified GPS recordings
• ▸Elevation — SRTM digital elevation model data for consistent, high-quality profiles
• ▸Weather — Open-Meteo API for race-day forecasts and historical conditions