The short answer
Set the treadmill to 1% incline and the belt speed to your outdoor pace. The speed in km/h is 60 divided by your pace in minutes per km: 5:00 per km is 12.0 km/h (7.5 mph), and 6:00 per km is 10.0 km/h (6.2 mph). For speed in mph, divide km/h by 1.609.
When you change the incline, change the speed too, or the effort will not match. The calculator below does both, and the tables underneath give the numbers for common paces.
Convert your pace
Equal effort means equal oxygen cost. At 1% the belt speed equals your outdoor speed; steeper grades need a slower belt.
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Pace to belt speed at 1% incline
| Pace /km | Pace /mile | Speed km/h | Speed mph |
|---|---|---|---|
| 3:30 | 5:38 | 17.1 | 10.7 |
| 3:45 | 6:02 | 16.0 | 9.9 |
| 4:00 | 6:26 | 15.0 | 9.3 |
| 4:15 | 6:50 | 14.1 | 8.8 |
| 4:30 | 7:15 | 13.3 | 8.3 |
| 4:45 | 7:39 | 12.6 | 7.8 |
| 5:00 | 8:03 | 12.0 | 7.5 |
| 5:15 | 8:27 | 11.4 | 7.1 |
| 5:30 | 8:51 | 10.9 | 6.8 |
| 5:45 | 9:15 | 10.4 | 6.5 |
| 6:00 | 9:39 | 10.0 | 6.2 |
| 6:15 | 10:04 | 9.6 | 6.0 |
| 6:30 | 10:28 | 9.2 | 5.7 |
| 6:45 | 10:52 | 8.9 | 5.5 |
| 7:00 | 11:16 | 8.6 | 5.3 |
| 7:30 | 12:04 | 8.0 | 5.0 |
| 8:00 | 12:52 | 7.5 | 4.7 |
Set the incline to 1% for every row. Speeds are rounded to 0.1, which is the step on most belts.
Why 1%, and why it is not always the right number
Outdoors, you push against air. On a belt you do not, so running on the flat feels easier than the same speed outside. Research on treadmill running in the 1990s found that a 1% grade closely restores the missing cost at normal training speeds. That is the rule used on this page.
The air-resistance effect grows with speed, so it matters most for fast running and very little when you jog. If you are moving slowly, 0% to 0.5% is fine. For interval work at 4:30 per km or quicker, 1% is the safe default.
Keep the effort equal at other inclines
A steeper grade costs more energy at the same speed, so the belt has to slow down to keep the effort the same. Each row below is an outdoor pace; read across to see the belt speed that matches it at each grade. The 1% column equals your outdoor speed.
Belt speed in km/h
| Outdoor pace /km | 0% | 1% | 2% | 3% | 4% | 5% | 6% | 8% |
|---|---|---|---|---|---|---|---|---|
| 4:00 | 15.7 | 15.0 | 14.4 | 13.8 | 13.3 | 12.8 | 12.3 | 11.5 |
| 4:30 | 13.9 | 13.3 | 12.8 | 12.3 | 11.8 | 11.4 | 11.0 | 10.2 |
| 5:00 | 12.5 | 12.0 | 11.5 | 11.0 | 10.6 | 10.2 | 9.9 | 9.2 |
| 5:30 | 11.4 | 10.9 | 10.5 | 10.0 | 9.7 | 9.3 | 9.0 | 8.4 |
| 6:00 | 10.5 | 10.0 | 9.6 | 9.2 | 8.9 | 8.5 | 8.2 | 7.7 |
| 6:30 | 9.6 | 9.2 | 8.8 | 8.5 | 8.2 | 7.9 | 7.6 | 7.1 |
| 7:00 | 9.0 | 8.6 | 8.2 | 7.9 | 7.6 | 7.3 | 7.1 | 6.6 |
Belt speed in mph
| Outdoor pace /km | 0% | 1% | 2% | 3% | 4% | 5% | 6% | 8% |
|---|---|---|---|---|---|---|---|---|
| 4:00 | 9.7 | 9.3 | 8.9 | 8.6 | 8.3 | 8.0 | 7.7 | 7.2 |
| 4:30 | 8.7 | 8.3 | 7.9 | 7.6 | 7.3 | 7.1 | 6.8 | 6.4 |
| 5:00 | 7.8 | 7.5 | 7.1 | 6.9 | 6.6 | 6.4 | 6.1 | 5.7 |
| 5:30 | 7.1 | 6.8 | 6.5 | 6.2 | 6.0 | 5.8 | 5.6 | 5.2 |
| 6:00 | 6.5 | 6.2 | 6.0 | 5.7 | 5.5 | 5.3 | 5.1 | 4.8 |
| 6:30 | 6.0 | 5.7 | 5.5 | 5.3 | 5.1 | 4.9 | 4.7 | 4.4 |
| 7:00 | 5.6 | 5.3 | 5.1 | 4.9 | 4.7 | 4.5 | 4.4 | 4.1 |
The formula behind both tables: belt speed = outdoor speed × 0.209 ÷ (0.2 + 0.009 × grade in percent). The 0.2 is the cost of running one metre on the flat; each percent of grade adds 0.009 to it.
Worked example
You want 6 × 90 seconds hard on a hill, at the effort of 5:00 per km. Outdoors that pace is 12.0 km/h. On a 5% grade the matching belt speed is 10.2 km/h, which the belt shows as 5:52/km. Rest between reps at 1% and a walking or easy jogging speed.
Set it up and check it
- Choose the speed first, then the incline, and confirm both before the rep starts.
- Return to 1% incline for rests and warm-up.
- If a session feels harder than the table says, check the room heat before you slow the belt. A fan makes a large difference.
- Check the belt: at 10 km/h it travels 166.7 metres a minute. Divide by the loop length in metres to get the turns per minute you should see on a marked spot.
Ready to put numbers on a whole season? The indoor workout builder sets every interval from your race time, and six treadmill interval sessions shows what to do with them.
Questions
What incline matches outdoor running?
1%. Studies comparing treadmill and outdoor running found that a 1% grade closely matches the effort of running on the flat outdoors at normal training speeds, because it makes up for the missing air resistance. At very slow jogging speeds you can use 0% to 0.5%.
Is 5:00 per km the same as 12 km/h?
Yes. Speed in km/h is 60 divided by the pace in minutes per km, so 5:00 per km is 12.0 km/h, or 7.5 mph. Set 1% incline and it matches 5:00 per km outdoors.
How do I convert mph to minutes per mile?
Divide 60 by the mph figure. 7.5 mph is 8.0 minutes per mile, which is 8:00.
Why does the treadmill feel harder than outdoors?
Heat is the main reason: with no airflow your body cools less well, so heart rate drifts up. A fan in front of you and a lower room temperature close most of the gap. Differences in the belt surface and in the feel of pace also play a part.
Does adding incline change my pace?
Yes. A steeper grade costs more energy at the same speed, so the same effort needs a slower belt. At 5% the belt runs about 15% slower than at 1% for the same effort. The second table gives the speed for each grade.
Can I trust the speed my treadmill shows?
Most belts are close, but some read a few percent high or low. Mark the belt, count how many times the mark passes in a minute at 10 km/h, and compare with the loop length: 166.7 metres per minute divided by the loop length in metres.
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