Yasso 800s Marathon Time Predictor
Convert your 800-meter repeat time into a predicted marathon finish time using the Yasso 800s rule, with the implied marathon pace. Runs in your browser.
The time you can average for a workout of about 10 × 800m repeats, with equal-time jog recovery.
Implied marathon pace ≈ 8:01 /mi. The Yasso rule maps an 800m time of 3:30 (min:sec) to a marathon of 3:30 (hours:min).
About this tool
Yasso 800s are a popular marathon-prediction workout devised by Bart Yasso of Runner's World. The rule is elegantly simple: the average time you can run a set of about ten 800-meter repeats — expressed in minutes and seconds — predicts your marathon time in hours and minutes. Run your 800s in 3 minutes 30 seconds each and the rule predicts a 3 hour 30 minute marathon; run them in 2:50 and it predicts 2:50. This tool applies that mapping and also shows the implied average marathon pace per mile so you can sanity-check it against your training. It is a rule of thumb, not a guarantee: it tends to be optimistic for runners whose endurance lags their speed and conservative for well-trained marathoners, and it assumes you have done the long-run mileage to actually hold the pace for 26.2 miles. Use it as a training benchmark and a goal-setting aid, not a promise. Everything is computed locally.
How to use it
- Run a workout of roughly 10 × 800m repeats with equal-time jog recovery.
- Enter the average time per 800m in minutes and seconds.
- Read the predicted marathon time and the implied per-mile pace.
- Repeat the workout through training to track progress toward your goal.
Frequently asked questions
- What exactly are Yasso 800s?
- A marathon-prediction and training workout from Bart Yasso (Runner's World): you run 800-meter repeats at an effort where the time in minutes:seconds equals your goal marathon time in hours:minutes, building up to about ten repeats with equal-time recovery jogs.
- How is the marathon time predicted?
- Directly from your 800m time by reinterpreting the units: a 3:30 (3 min 30 s) 800 predicts a 3:30 (3 hr 30 min) marathon. The tool also converts that to an average pace per mile so you can compare it to your long runs.
- How accurate is the prediction?
- It is a well-known rule of thumb, not a precise model. Studies and coaches note it can be optimistic — especially for runners with strong speed but limited endurance — and it only holds if your weekly mileage and long runs support racing 26.2 miles at that pace. Treat it as a benchmark.
- How much recovery should I take between repeats?
- The classic protocol uses equal-time recovery: jog easily for the same duration it took to run the 800. So 3:30 repeats get about 3:30 of recovery jog. The repeats should feel hard but repeatable, not all-out.
- Should I trust this over a recent race result?
- A recent half marathon or 10K is generally a better predictor of marathon fitness than a track workout. Use Yasso 800s as a complementary training session and a motivating progress check, and cross-reference with race-based predictors.
- Is this medical or coaching advice?
- No. It is an informational running calculator. Build mileage gradually, and consult a coach or physician before starting intense interval training, especially if you are new to running or have health concerns.