The idea
A percentage plan writes each session as a fraction of race pace: 100% is that pace, 90% is slower and 105% is faster. The same plan serves a 50:00 runner and a 34:00 runner. Both do “6 x 1000 m at 102%” and take on a similar relative load, each at their own pace.
The reference pace belongs to the plan’s distance: 10K pace in a 10K plan, half marathon pace in a half marathon plan. Each percentage means something different at each distance, as the sections below show.
The formula
Session pace = race pace x (2 - percentage/100)
Work in seconds per kilometer. With a race pace of 4:00 (240 s):
- At 90%: 240 x 1.10 = 264 s = 4:24
- At 105%: 240 x 0.95 = 228 s = 3:48
Another example: 90% of 5:00 is 5:30, because 5:00 plus 10% is 30 seconds.
Why use pace and not speed
You can define the percentage on speed: 90% of speed means dividing the pace by 0.90. At 5:00/km that gives 5:33, against 5:30 from the formula above.
Near 100% the two methods almost agree. At the extremes they part: at 80%, with a 5:00 pace, speed gives 6:15 and pace gives 6:00.
Calculating on pace has two advantages. Each percentage point is a fixed number of seconds (2.4 s/km at 4:00), so you can do the math in your head. And 95% and 105% sit at equal distances from 100%. PaceSpan uses this Canova-style convention.
Pace chart
Values for a 40:00 10K (4:00/km), with the approximate equivalent in a 10K plan:
| % | Pace | Close to | Typical use |
|---|---|---|---|
| 80 | 4:48 | Moderate long run | Basic endurance |
| 85 | 4:36 | General pace | Progression runs, long runs |
| 90 | 4:24 | Marathon pace | Long fast run, special continuous run |
| 95 | 4:12 | Half marathon pace | Long specific continuous runs |
| 100 | 4:00 | 10K pace | Specific intervals |
| 105 | 3:48 | Near 5K pace | Specific speed |
| 110 | 3:36 | Near 1500 m pace | Short repetitions |
| 115 | 3:24 | Faster than 1500 m | General speed, 150-300 m |
The equivalents depend on the runner and on the plan’s distance. In a 5K plan they shift: 95% of 5K pace equals 10K pace, so a long continuous run there is race effort and lasts a short time. In a marathon plan, 90% of marathon pace sits between an easy run and aerobic threshold.
Worked example
Session: 3 km warm-up, 6 x 1000 m at 102% with 2 min jog recovery, and a 2 km cool-down.
- The factor is 2 - 1.02 = 0.98.
- 240 s x 0.98 = 235.2 s per kilometer.
- Each repetition runs at 3:55.
- Six repetitions add up to 6 km of work in about 23:30.
Other repetitions for the same runner:
- 600 m at 102%: 2:21
- 400 m at 105%: 1:31
- 300 m at 110%: 1:05
- 2000 m at 100%: 8:00
From 5K pace to 10K pace
The formula also gives you a quick estimate across distances. A runner with 19:15 for 5K runs 3:51/km. Their 95% is 3:51 x 1.05 = 4:02, close to the 4:00 they hold in a 40:00 10K. So a long continuous run at 95% of 5K pace is 10K effort, about 40 minutes at most.
The same reading works in reverse. If your plan is a 10K plan and a session calls for 105%, you run near your 5K pace. You can manage repetitions of 400 m at that pace with long recovery. Six kilometers in a row will break you.
A week in percentages
For the 4:00/km runner, a special-phase week can contain:
- A 12 km continuous run at 90%: 4:24/km.
- 8 x 400 m at 105%: 1:31 each.
- A 15 km long fast run at 87.5%: 4:30/km.
- Easy runs below 80%: slower than 4:48/km.
Which reference pace to use
Set the 100% at the pace of a recent race in good condition, or at the estimate from another distance in the calculator. Follow two rules:
- If your result is old or you are returning from a break, use a pace 2-3% slower until you run a recent test.
- If your goal sits far above your current fitness, train with your current pace. Raise the reference when you improve.
Percentages in a longer race
The same logic applies to a half marathon or marathon plan, but the numbers shift. For a runner whose half marathon pace is 4:12/km, 90% is 4:37, 95% is 4:25 and 105% is 3:59. The sessions look the same on paper (a block at 100%, a float at 90%, a long run at 92%), but each percentage lands on a different pace because the reference pace differs. A percentage only means something next to the distance of its plan.
Common mistakes
Applying the percentage to easy runs. Below 80% you run by feel. An easy run at 70% of a 40:00 10K comes out at 5:12, and you can go slower.
Ignoring terrain and wind. Percentages hold on flat ground without strong wind. On hills or in wind, keep the effort and let the pace move.
Measuring slow runners by distance alone. For long fast runs, total time matters as much as kilometers, so count minutes.
Mixing steps that sit far apart. A session with paces more than 5% apart needs a reason, such as a cut-down. Without one, split the work across two days.
From percentages to a plan
Percentages define the type of effort. The plan decides when and how much. The calculator gives you the full pace table for your result. To get a week-by-week plan, create it from the home page.
Frequently asked questions
How do I calculate 90% of my race pace?
Multiply your pace in seconds per kilometer by (2 - 90/100) = 1.10. With a 4:00 pace (240 s), 240 x 1.10 = 264 s, which is 4:24. For 105%, the factor is 0.95: 240 x 0.95 = 228 s, or 3:48.
Why not divide the pace by the percentage?
Dividing takes a percentage of speed. Near 100% the gap is a couple of seconds, but it grows at the extremes and breaks the symmetry: 95% and 105% no longer sit at the same distance from 100%. With pace, every percentage point is worth the same number of seconds.
Is 100% my personal best or my goal?
Use the pace you can hold today at that distance, from a recent race or an honest estimate. If your goal sits 3-5% above your current fitness, start from the current number and raise the 100% as you improve.
What pace is 95% of 5K pace?
Close to 10K pace. A long continuous run at that percentage is race effort, and you can hold it only for a short time.