Race time predictor (VDOT calculator)
Enter a time you ran on a known distance and get your predicted times on every other distance. Built on the Jack Daniels VDOT tables.
Enter your reference performance
Understanding VDOT and race time prediction
VDOT is an aerobic fitness index created by US running coach Jack Daniels. It's based on the idea that a runner at a given fitness level produces proportional performances across all distances, provided their training is appropriate for each distance.
Concretely, if you run a 10K in 45 minutes, your VDOT is around 45. The VDOT tables then give you a reliable estimate of your potential on 5K, half marathon, marathon, and so on. It's a tool used by coaches around the world to plan training and set realistic goals. To go further, you can also estimate your MAS and derive your training paces.
How to use this race predictor
Select the distance for which you have a recent and reliable performance (ideally a race).
Enter your finish time in hours, minutes, and seconds.
The calculator finds your VDOT and shows your predicted times across all distances, from 1500m to the marathon.
VDOT vs Riegel formula
Two main approaches exist for predicting race times from a single performance.
Jack Daniels VDOT
Built on real physiological data: VO2max, lactate threshold, race-specific running economy. More accurate, especially across very different distances. Used by coaches worldwide. This is what powers our calculator.
Riegel formula
T2 = T1 × (D2 / D1)^1.06. Simple math, easy to compute by hand. Drifts on big distance gaps (5K to marathon). The 1.06 exponent assumes a generic durability curve that doesn't match every runner.
Frequently asked questions
What is VDOT?
VDOT is a fitness index developed by coach Jack Daniels. It lets you compare performances across different distances and predict race times. A VDOT of 40 corresponds to a marathon in around 3:50, while a VDOT of 60 corresponds to a marathon in around 2:43.
How does the race time prediction work?
From a time you ran on a known distance, the calculator finds your VDOT (your performance level). It then uses Jack Daniels VDOT tables to estimate your times across all the other distances, assuming distance-specific training.
How accurate are race time predictions?
Predictions are reliable when your training is balanced. A runner who only trains short will overestimate their marathon. Conversely, a well-trained marathoner can run faster than predicted on 5K. VDOT tables assume race-specific training for the target distance.
Which reference distance should I pick?
Use your most recent and most reliable performance, ideally a race result. A 10K time is a good compromise: long enough to be aerobic, short enough to race regularly. Avoid using a training time, race conditions give more accurate results.
How does VDOT compare to the Riegel formula?
Riegel (T2 = T1 × (D2/D1)^1.06) is a simple mathematical approximation. The VDOT tables from Jack Daniels are based on real physiological data and are more accurate, especially for big distance gaps (e.g. 5K to marathon).
How does the 1 mile compare to 1500m?
1 mile (1609m) is roughly 6 to 7% longer than 1500m. So your 1 mile time is slightly slower than your 1500m time. As a quick conversion: VDOT 50 corresponds to 5:24 on 1500m and around 5:48 on 1 mile. The 1500m results from this calculator are a close proxy for 1 mile pace.
Related tools
MAS calculator
Estimate your Maximal Aerobic Speed (vVO2max) and your training paces.
Pace calculator
Convert pace and speed (km/h, min/km, min/mile) for every session.
Heart rate zones
Calibrate session intensity with your 5 HR zones.
Pace strategy
Plan your race pace segment by segment based on the elevation profile.
Start free
Set a realistic race goal and let Kopilo adapt your plan week after week.