Treadmill Incline and Calories Burned: The ACSM Walking Equation
October 29, 2026
Incline walking is a low-impact way to increase the energy cost of a workout. The American College of Sports Medicine (ACSM) walking equation estimates oxygen consumption (VO₂, in mL per kg per minute): VO₂ = 0.1 × speed + 1.8 × speed × grade + 3.5, where speed is in meters per minute and grade is a fraction (10% = 0.10). The 0.1 term is horizontal walking, the 1.8 term is the vertical component, and 3.5 is resting oxygen use.
To convert to calories: kcal per minute = VO₂ × body weight in kg ÷ 1,000 × 5, since roughly 5 kcal are burned per liter of oxygen. A speed of 3.5 mph is 3.5 × 26.82 = 93.9 meters per minute.
Skip the math and get your answer instantly:
Open the Calories Burned Calculator →Worked Table for an 80 kg Person at 3.5 mph
At 0% grade: VO₂ = 0.1 × 93.9 + 3.5 = 12.9 mL/kg/min, and energy use = 12.9 × 80 ÷ 1,000 × 5 = 5.16 kcal per minute, or 309 per hour. At 10% grade: VO₂ = 9.39 + 1.8 × 93.9 × 0.10 + 3.5 = 29.8, and energy use = 11.9 kcal per minute, or 715 per hour. Incline more than doubles the cost of walking at the same speed. Note that the gross figures include resting metabolism (the 3.5 term); net calories above resting are about 1.4 kcal per minute lower for this person.
The equation is validated for walking speeds from about 1.9 to 3.7 mph (50 to 100 m/min) and grades up to about 15%. For running speeds, a different equation applies (0.2 × speed instead of 0.1).
| Grade | VO₂ (mL/kg/min) | kcal per minute | kcal per hour |
|---|---|---|---|
| 0% | 12.9 | 5.2 | 309 |
| 5% | 21.3 | 8.5 | 512 |
| 10% | 29.8 | 11.9 | 715 |
| 15% | 38.2 | 15.3 | 918 |
Practical Use
A 30-minute walk at 3.5 mph and a 10% incline burns about 357 calories for an 80 kg person, compared with 155 on the flat. If you can't maintain the speed at a steep grade, drop the speed: 3.0 mph (80.5 m/min) at 10% gives VO₂ = 8.05 + 14.5 + 3.5 = 26.0, which is 10.4 kcal per minute. Hold the handrails lightly or not at all, because gripping them reduces the effective workload and makes the calculation overestimate.
Heavier and Lighter People
Energy use scales with body weight. For a 60 kg person at 3.5 mph and 10% incline, the cost is 29.8 × 60 ÷ 1,000 × 5 = 8.9 kcal per minute, and for a 100 kg person it is 14.9. To find your own number, plug your weight into the formula. Fitness trackers' estimates can differ because they use heart rate and other assumptions.
Safety and Progression
Increase incline gradually, because the calves, Achilles tendons, and hamstrings work harder. A common progression is adding 1 to 2 percentage points of incline per week. People with knee, ankle, or balance problems should be careful at steep inclines. This article offers estimates, and individual results vary.
Frequently Asked Questions
What is the ACSM walking equation?
VO₂ = 0.1 × speed + 1.8 × speed × grade + 3.5, with speed in m/min and grade as a fraction.
How do I convert VO₂ to calories?
kcal/min = VO₂ × kg ÷ 1,000 × 5.
How much does incline raise the calories burned?
In the example, a 10% grade more than doubles the energy cost of walking at 3.5 mph.
Does holding the handrails matter?
Yes, it reduces the workload and makes the estimate too high.
What speeds does the equation cover?
Roughly 1.9 to 3.7 mph.