About RunMath

RunMath is a small set of free calculators for runners, built around one idea: the numbers behind a race plan should take a minute to find, not a scroll past a long article or a sign-up form.

Each tool does one job. The race time predictor turns a recent race into realistic times at other distances; the running pace calculator turns a goal time into the pace and splits to run it; the VDOT calculator sets your training paces; the treadmill pace calculator converts speed to pace and allows for incline; and the Yasso 800 calculator turns a marathon goal into a workout. The formulas behind every tool are shown on its page, so you can check the math yourself.

Pace arithmetic is exact. Race predictions and training paces use published models: Pete Riegel's formula, Dave Cameron's model and the Daniels–Gilbert equations behind Jack Daniels' VDOT. Rather than pick one, the predictor shows all three and the range between them, and says plainly when a prediction is a stretch.

All calculations run entirely in your browser. Nothing you type is sent to a server or stored by us.

Spotted an error, or want a calculator we don't have yet? We'd genuinely like to know. This site improves through feedback from runners in the middle of a training block.