Apply the traditional Yasso 800 rule in either direction: an average repeat time or a marathon goal. This training heuristic does not guarantee an individual race result.
Yasso 800 Marathon Predictor Formula
MT = T800 * 60
T800 = MT / 60
MP = MT / (42195 / 1609.344)
- MT is the predicted marathon finish time in seconds
- T800 is the average time per 800m repeat in seconds
- MP is the marathon pace in seconds per mile (divide MT by 42.195 instead for seconds per kilometer)
The Yasso 800 rule, popularized by Bart Yasso of Runner’s World, says that the minutes and seconds of your average 800m repeat become the hours and minutes of your marathon. If you can run 10 x 800m averaging 3:30 per rep, the method predicts a 3:30:00 marathon. Multiplying the 800m time in seconds by 60 is the same conversion written as a formula.
The calculator works in both directions. The predict mode applies the first formula to your average 800m time and returns your projected finish time, marathon pace per mile and per kilometer, the equal-time recovery jog, and the total length of a full 10-rep session. The target mode applies the second formula to a goal marathon time and returns the traditional 800m target corresponding to that goal. Session totals show both nine between-rep jogs and ten jogs including a final recovery, excluding warm-up and cool-down. The optional mileage setting retains the original tool’s additions as illustrative assumptions, not validated prediction intervals.
Yasso 800 Times and Illustrative Finish Scenarios
The first table converts common repeat times into the raw rule and matching marathon pace. The last column illustrates adding 5 to 15 minutes. These additions are assumptions, not typical outcomes established by the rule.
| Average 800m time | Raw Yasso prediction | Marathon pace | Illustrative +5–15 min scenario |
|---|---|---|---|
| 2:40 | 2:40:00 | 6:06 /mi | 2:45 to 2:55 |
| 3:00 | 3:00:00 | 6:52 /mi | 3:05 to 3:15 |
| 3:20 | 3:20:00 | 7:38 /mi | 3:25 to 3:35 |
| 3:30 | 3:30:00 | 8:01 /mi | 3:35 to 3:45 |
| 3:45 | 3:45:00 | 8:35 /mi | 3:50 to 4:00 |
| 4:00 | 4:00:00 | 9:09 /mi | 4:05 to 4:15 |
| 4:30 | 4:30:00 | 10:18 /mi | 4:35 to 4:45 |
| 5:00 | 5:00:00 | 11:27 /mi | 5:05 to 5:15 |
| 5:30 | 5:30:00 | 12:35 /mi | 5:35 to 5:45 |
The second table preserves the original mileage and long-run scenarios for context. Its minute additions are assumed examples; weekly distance or a longest run alone cannot establish readiness, predict an individual finish, or set race pace.
| Weekly mileage | Longest run | Illustrative context | Assumed addition |
|---|---|---|---|
| Under 30 mi (48 km) | Under 16 mi | Endurance may differ from repeat speed | 15 to 25 min (assumed) |
| 30 to 40 mi (48 to 64 km) | 16 to 18 mi | Compare with endurance training and recent races | 10 to 15 min (assumed) |
| 40 to 55 mi (64 to 89 km) | 18 to 20 mi | A scenario, not a confirmed race goal | 5 to 10 min (assumed) |
| 55+ mi (89+ km) | 20 to 22 mi | High volume alone does not validate the estimate | 0 to 5 min (assumed) |
Example Problems
Example 1: Predict a marathon time from 800m repeats. You run 10 x 800m on the track and average 3:30 per rep. Convert the rep time to seconds: 3*60 + 30 = 210 seconds. Multiply by 60: MT = 210 * 60 = 12,600 seconds, which is 3:30:00. The matching pace is 12,600 / (42195 / 1609.344) = 481 seconds per mile, about 8:01 /mi. Selecting the original 30 to 40 miles/week scenario adds an assumed 10 to 15 minutes, giving 3:40 to 3:45. This is an illustration, not a validated race-day interval.
Example 2: Find the 800m target for a goal marathon. Your goal is a 4:00:00 marathon. Convert to seconds: MT = 14,400. Divide by 60: T800 = 14,400 / 60 = 240 seconds, so each 800m repeat should take 4:00 with a 4:00 recovery jog between reps. Start with 4 reps in an early-season session and add one rep per week until you can complete all 10 at 4:00, which is about 8:03 per mile of fast running against a 9:09 per mile race pace.
FAQ
Why was my marathon slower than the Yasso prediction? The workout measures speed over 800m intervals, which depends heavily on VO2 max, while the marathon depends on aerobic endurance, fuel storage, and running economy. A runner can have the speed for fast reps without the endurance to hold goal pace past 20 miles. Use the raw estimate alongside your training history and recent race evidence. The optional mileage additions are illustrative assumptions rather than a validated correction model.
Should I run the 800s faster than my goal time suggests? The formula supplies a traditional benchmark, not an instruction to run faster for a fixed buffer. Keep the workout appropriate to your training plan. Neither hitting the target nor applying the illustrative mileage additions establishes race pace.
What should the recovery between repeats be? The original workout uses a recovery jog equal in time to the rep itself, so a 3:30 rep gets a 3:30 jog. Some plans substitute a 400m jog, which shortens the rest for most runners and makes the session harder. Changing recovery changes the workout, so record the format consistently when comparing sessions. It does not supply a quantified change in marathon prediction.
