Built by Tommo, Verus founder — free to use, no account required.
Treadmill Pace Converter
What your belt speed and incline are actually worth outside.
Treadmill Pace Converter
Turn belt speed and incline into the outdoor pace that costs the same effort.
Belt pace
5:60 /km
9:39 /mile
Flat-equivalent pace
5:44 /km
9:14 /mile
A 1% incline is worth 4.5% more speed at the same oxygen cost.
What each incline is worth at this speed
| Incline | Flat pace /km | Effort gain |
|---|---|---|
| 0% | 5:60 | +0.0% |
| 0.5% | 5:52 | +2.3% |
| 1% | 5:44 | +4.5% |
| 1.5% | 5:37 | +6.8% |
| 2% | 5:30 | +9.0% |
| 3% | 5:17 | +13.5% |
| 4% | 5:05 | +18.0% |
| 5% | 4:54 | +22.5% |
| 6% | 4:43 | +27.0% |
| 8% | 4:25 | +36.0% |
| 10% | 4:08 | +45.0% |
Derived from the ACSM metabolic equation for running, which puts the oxygen cost at 0.2 × speed + 0.9 × speed × grade + 3.5. Setting a graded run equal to a flat one gives a flat-equivalent speed of speed × (1 + 4.5 × grade) — so every 1% of incline is worth 4.5% more speed, with no fudge factor involved. It models oxygen cost, not wind resistance, heat, or how a belt feels different underfoot.
Use It On A Real Race
About This Tool
Every runner who has moved a session indoors has asked the same question: what is this actually worth? The usual answer is folklore — set the incline to 1% and call it even. This converter answers it from the ACSM metabolic equation for running instead, which gives the oxygen cost of running at a given speed and grade. Set the oxygen cost of a graded run equal to that of a flat one, solve for the flat speed, and you get a conversion with no fudge factor in it at all: every 1% of incline is worth 4.5% more speed.
How To Use It
- Choose kph or mph to match what your treadmill displays.
- Enter the belt speed and the incline you are running at.
- Read the flat-equivalent pace — the outdoor pace that costs the same oxygen.
- Use the reference table to see what every common incline setting is worth at that speed.
- Below about 8 kph the running equation is outside its validated range, and the tool says so rather than pretending otherwise.
Where the conversion comes from
Most treadmill conversions you will find are rules of thumb passed between runners. This one is derived, and the derivation is short enough to show.
The ACSM metabolic equation for running gives the oxygen cost of running at a speed S in metres per minute on a fractional grade G:
The equation
VO2 = 0.2 × S + 0.9 × S × G + 3.5. The first term is the cost of moving horizontally, the second the cost of lifting yourself, and 3.5 is what you burn standing still.
To find the flat speed that costs the same oxygen, set the graded version equal to the flat version and solve. The 3.5 cancels, and so does most of the rest: S_flat = S × (1 + 4.5 × G). Every 1% of incline is worth 4.5% more speed, and that number falls out of the ratio between the vertical and horizontal terms rather than being chosen by anybody.
What each speed is worth
Flat-equivalent pace at a 1% incline, the most commonly used setting.
| Belt speed | Pace on the flat | Flat-equivalent at 1% |
|---|---|---|
| 8 kph | 7:30 /km | 7:11 /km |
| 9 kph | 6:40 /km | 6:23 /km |
| 10 kph | 6:00 /km | 5:44 /km |
| 11 kph | 5:27 /km | 5:13 /km |
| 12 kph | 5:00 /km | 4:47 /km |
| 14 kph | 4:17 /km | 4:06 /km |
| 16 kph | 3:45 /km | 3:35 /km |
The gap widens with incline rather than speed. At 12 kph on a 5% grade, the belt is showing 5:00 per kilometre and the effort is worth 4:05 — nearly a minute a kilometre, which is the difference between an easy run and a threshold session.
The 1% convention, examined
The advice to set 1% to simulate outdoor running is close to universal and rarely questioned. It deserves questioning.
It originates in research on the energy cost of overcoming air resistance outdoors, which a treadmill removes. That effect is real — but it scales with the square of velocity, so it matters considerably more to a runner at 16 kph than to one at 9 kph. Applying a single 1% correction across all speeds applies the same adjustment to runners for whom the underlying effect differs by a factor of three.
By this equation, 1% is worth 4.5% more speed. For a runner at 10 kph that turns a 6:00 kilometre into a 5:44 one — a sixteen-second adjustment for an air-resistance effect that, at that speed, is small. Many recreational runners would be better served by 0 to 0.5%.
The practical version
If you are running fast, 1% is reasonable. If you are running at recreational paces, it probably overcompensates, and 0.5% or a flat belt is closer to honest. None of this matters much for an easy run — it matters when you are trying to hit a specific pace for a specific session.
What the conversion does not model
It converts oxygen cost, and oxygen cost is not the whole of how hard a run feels. Four things it deliberately leaves out:
- Heat. Indoor air is still, so evaporative cooling is much worse than running outdoors at the same pace. A treadmill session frequently raises core temperature faster than the equivalent outdoor one, and that is often what makes it feel harder rather than the pace.
- Belt mechanics. The belt moves underneath you, which changes the demand on your hamstrings slightly and assists leg turnover. The effect is small but it is real, and it is why treadmill and outdoor running feel different at identical converted paces.
- Terrain. No cambers, no corners, no potholes, no wind on your side. Good for controlled sessions, poor for race specificity.
- Calibration. Treadmill speed displays drift, particularly on well-used machines. If your treadmill paces look implausibly good compared with your outdoor running, suspect the belt before the physiology.
Using a treadmill well
- 1 Use it for controlled work — intervals at an exact pace, progression runs, tempo efforts where drifting off pace is the usual failure.
- 2 Use it for hills if you do not have any. A sustained 5-8% grade is a session most flat-country runners cannot otherwise do.
- 3 Do not do all your long runs on it. Durability is partly a function of varied ground, and a marathon is not run on a belt.
- 4 Set the incline deliberately rather than by habit, now that you know what each setting is worth.
- 5 Have a fan on you. It is the single cheapest improvement to indoor running there is.
Related Tools
Frequently Asked Questions
What incline should I set on a treadmill to simulate outdoor running?
The widespread advice is 1%, which by the ACSM equation is worth about 4.5% more speed — a bigger adjustment than most people intend. The 1% convention comes from research at faster running speeds where wind resistance is meaningful; at typical recreational paces it likely overcompensates. Many runners are better served by 0 to 0.5%.
How do you convert treadmill pace to outdoor pace?
Multiply belt speed by (1 + 4.5 × grade), where grade is the fractional incline — so 2% is 0.02. That comes straight from setting the ACSM running equation for a graded run equal to the same equation for a flat run and solving for flat speed. This tool does the arithmetic and shows the result in min/km and min/mile.
Is running on a treadmill easier than running outside?
At the same speed on a flat belt, marginally — you are not overcoming air resistance, and the belt removes any need to generate forward propulsion against variable ground. The difference is small at recreational paces and grows with speed. Perceived difficulty is a separate question, and most people find the treadmill harder mentally and cooler-feeling despite the lack of airflow.
Why does 1% incline equal 4.5% more speed?
Because of the ratio of the two terms in the ACSM running equation. The horizontal cost of running is 0.2 × speed and the vertical cost is 0.9 × speed × grade, so the vertical term is 4.5 times as expensive per unit. That ratio, and nothing else, is where the number comes from.
Does this account for heat on a treadmill?
No, and that is a real limitation. Indoor running usually means still air and no evaporative cooling from movement, so a treadmill session at a given pace often feels harder and raises core temperature faster than the same pace outdoors. The conversion models oxygen cost only — use the heat-adjusted pace calculator for the thermal side.
Is treadmill running good training for a race?
It is genuinely useful for controlled sessions, hill work you have no hills for, and running when the alternative is not running. The gap is specificity: no wind, no cambers, no corners, no variable surface, and a belt that assists leg turnover slightly. Do some of your training outdoors on ground like the race, particularly the long runs.