Yasso 800s Calculator
Enter a goal marathon time to get a target average 800 m repeat pace, or enter an average 800 m repeat time to get a predicted marathon time.
Mode
Target 800 m repeat time
Suggested session: 10 × 800 m at that pace, with a 3:30 jog recovery (equal time) between repeats.
This estimate uses a generic formula. Connect your Strava/Whoop/Garmin data for a version personalised to your actual training.
Get early accessWhere the rule comes from
Runner's World columnist and coach Bart Yasso popularised a simple mnemonic in the 1990s: run 800 m repeats averaging the same time, in minutes and seconds, as your goal marathon time in hours and minutes. A 2 hour 50 minute marathon goal pairs with a 2 minute 50 second average 800. Ten repeats, with a recovery jog of equal time between each, is the session most commonly attached to the rule.
How honest is this, really
Be clear about what this is: a coaching rule of thumb with no peer-reviewed validation behind it, not a fitted model. It works as well as it does mostly by coincidence of units, not physiology, and anecdotally it tends to run optimistic for marathoners who have not built the long run volume and marathon-specific endurance that the goal time assumes. Treat a Yasso prediction as one data point, not a target. Cross-check it against the Race Time Predictor using a recent race result, and against the Goal Time Reality Check before building a training block around it.
How to use the result
If you are working from a goal marathon time, the target 800 m pace and suggested session (10 repeats, equal-time recovery jog) give you a specific interval workout to test that goal against over a training block. If you are working from repeats you have already run, the predicted marathon time is a rough ceiling check on a goal, best used alongside a recent race result rather than on its own.
Sources and limitations: see our methodology.
Worked example
Take a runner targeting a 3:30:00 marathon.
The marathon goal's 3 hours and 30 minutes becomes 3 minutes and 30 seconds: a target average of 3:30 per 800 m, run as 10 × 800 m with a 3:30 jog recovery between each. Hitting that session consistently is one signal the goal is in range, not a guarantee.
FAQ
What is the Yasso 800s rule?
Coach Bart Yasso's rule of thumb says your average 800 m repeat time, in minutes and seconds, predicts your marathon finish time in hours and minutes. Average 2 minutes 50 seconds per 800 m, and the rule suggests a 2 hour 50 minute marathon.
How accurate is the Yasso 800s rule?
It has no peer-reviewed validation. It is a popular coaching mnemonic, not a fitted model, and it tends to run optimistic for marathoners who have not put in the long run volume and marathon-specific endurance a given goal time assumes. Use it as one rough data point, cross-checked with a recent race result.
How many Yasso 800 repeats should I run?
Ten repeats at the target pace is the session most commonly attached to the rule, with a recovery jog between each repeat lasting the same time as the repeat itself.
Should I train off a Yasso 800s prediction alone?
No. Treat it as a quick sanity check, not a training plan. Cross-check any Yasso prediction against the Race Time Predictor using a recent race result, and against the Goal Time Reality Check, before committing a training block to a goal time.
Why minutes and seconds for 800 m but hours and minutes for a marathon?
That unit shift is the entire trick behind the rule: it maps the two numbers you would already write down (an 800 m split, a marathon finish time) onto each other digit for digit, rather than relating them through pace or physiology.