How this instrument works
This instrument estimates VO2 from the oxygen-cost curve inside Jack Daniels and Jimmy Gilbert's Daniels-Gilbert formula, published in their 1979 training manual 'Oxygen Power: Performance Tables for Distance Runners.' Rather than requiring one fixed test, it works from any race actually run — a 5K time trial, a 10K, a half marathon or a marathon — converting the pace held into the oxygen cost the body was sustaining at that velocity.
That's the key difference from the Cooper 12-minute test on this site's VO2 Max Calculator: Cooper's formula needs one specific all-out effort, run for exactly 12 minutes, and reads VO2max straight off the distance covered. Daniels-Gilbert instead needs a race pace — distance divided by time gives velocity in metres per minute, and that velocity feeds a quadratic regression built from treadmill oxygen-consumption data, so any race of any length can be converted.
For shorter, harder races raced close to a runner's ceiling — a 5K or a strong 10K — the number this instrument returns sits close to a true VO2max. For a marathon, run at a pace sustainable for hours rather than minutes, the figure instead reflects the oxygen cost of that slower pace, not the runner's absolute ceiling, which is why Daniels' full VDOT system layers a second, duration-based adjustment on top of this same oxygen-cost equation to make race times comparable across distances.
- Enter Race distance (m) — the metric length of the race or time trial, e.g. 5000 for a 5K.
- Enter Race time (minutes) — your finish time, using decimals for seconds (20.5 for 20:30).
- Read Velocity (m/min) — the average pace held, in metres per minute.
- Read VO2 (ml/kg/min) — the oxygen cost of sustaining that velocity, per the Daniels-Gilbert equation.
- Compare results from different race distances to see how oxygen cost shifts with pace and duration.
Worked example — a 20:00 5K
Enter 5000 into Race distance (m) and 20 into Race time (minutes) — a 5,000 m race finished in exactly 20:00, a well-known milestone many club runners chase. Velocity reads 250 m/min, and VO2 reads 47.4645 ml/kg/min.
That comes from velocity = 5000 ÷ 20 = 250 m/min, then VO2 = −4.60 + (0.182258 × 250) + (0.000104 × 250²) = 47.4645. A marathoner covering 42,195 m in 2:30:00 (150 minutes) computes a velocity of 281.3 m/min and a VO2 of 54.8987 — a higher figure despite the much longer, less maximal effort, which is exactly why this raw oxygen-cost number isn't the same as a true VO2max for slower, longer races.
Questions
How is this different from the Cooper test VO2 Max calculator?
The Cooper calculator needs one specific test — an all-out 12-minute run, with VO2max read straight from the distance covered. This instrument instead works from any race actually raced, converting distance and time into velocity, then velocity into an oxygen-cost estimate through the Daniels-Gilbert equation, so a 10K, half marathon or marathon time all work just as well as a 5K.
Which race should I use to get the most accurate VO2 estimate?
A hard, well-paced effort somewhere between 5K and 10K, raced close to current fitness, tends to give the most representative figure — long enough to be aerobic, short enough to be close to maximal. A marathon time will still compute a VO2 figure, but because marathon pace is sustainable for hours rather than minutes, that number reflects the oxygen cost of marathon pace specifically, not necessarily an absolute ceiling.
Is this the same as VDOT?
Not quite — VDOT layers a second equation on top of this one, adjusting for how large a fraction of VO2max a runner can sustain for a race's specific duration, which is what lets Jack Daniels' tables convert a single race time into equivalent times at every other distance. This instrument computes just the underlying oxygen-cost figure, the same regression VDOT is built from, without that duration adjustment.
Does this work for distances other than 5K, 10K, half and full marathon?
Yes — enter any race distance in metres and any finish time in minutes, and the formula computes velocity and VO2 the same way regardless of distance, whether that's a 1500 m track race, an 8K cross-country course or an ultramarathon split. The equation itself doesn't care what the distance is called, only how fast it was covered.
Why does the formula use a quadratic term instead of a straight line?
Because the oxygen cost of running doesn't rise in a straight line with speed — air resistance, harder ground-contact forces and other mechanical costs mean each additional metre-per-minute of pace costs slightly more oxygen than the one before it. The 0.000104·v² term captures that upward curve; its effect is small at slower training paces but grows more noticeable at faster race speeds.