Yasso 800s Calculator

About this calculator

Yasso 800s is a marathon-predicting workout popularized by running coach Bart Yasso: run repeated 800 m intervals and note your average time in minutes and seconds, and — according to the rule of thumb — your marathon finish time in hours and minutes will land close to that same number (e.g., ten 800s averaging 3:30 each suggest a marathon around 3 hours 30 minutes). It is an informal, field-tested heuristic rather than a physiological formula, but it has held up well enough across decades of runners to remain a staple marathon-training benchmark.

Marathon runners use it mid-training-cycle as a fitness checkpoint and pacing guide — converting a goal marathon time into a concrete 800 m repeat target tells you exactly what pace to hit in a track workout, and running the workout and converting back tells you where your marathon fitness currently stands. It pairs naturally with marathon-pace runs, since both use the same target number as their anchor.

This calculator converts between a goal marathon time and the matching Yasso 800 repeat pace in either direction, and returns rep pace, marathon pace, and the total time and distance for a full Yasso workout.