Most runners ask which grade means it’s time to hike. The better question is how fast you’re moving up the slope. In a 2017 lab study at a 30-degree incline, walking cost less energy than running below about 0.7 meters per second, and the two matched at 0.8, according to the reported results.
In short: slow down past a certain point on a steep climb, and running stops paying off.
Why the hike-to-run threshold is a speed, not a grade
Your hike-to-run threshold is the point where walking uses less energy than running for the same climb. Start on level ground. Running costs about 3.40 joules per kilogram per meter, whatever your speed. Walking at its best costs about 1.64. Those figures come from Minetti’s 2002 study of 10 runners, as reported in its abstract. In short: on the flat, running costs about twice as much per meter, but you move far faster.
Now tilt the road. At a +45% grade, the same study reported walking at 17.33 and running at 18.93.
Translation: the steeper it gets, the less extra running costs you. The gap shrinks to almost nothing.
Think of a bike. On a flat road, the big ring is efficient. On a wall, the big ring forces you to grind, while the small ring spins easily. Running is your big ring. Hiking is your small ring. Where you switch depends on how fast you’re turning the pedals, not just on the slope.
Degrees vs percent grade: the conversion table nobody gives you
Lab papers use degrees. Your watch and your race profile use percent. Mixing them up wrecks the advice you read.
The formula is simple.
Percent grade = 100 * tan(angle in degrees)
Speed along slope = vertical speed / sin(angle)
Here’s the conversion at a fixed climbing rate of 0.35 meters per second. That’s 1,260 meters of climbing per hour, the vertical speed used in one vertical-kilometer study.
| Angle | Percent grade | Speed along slope at 0.35 m/s vertical | In km/h |
|---|---|---|---|
| 9.4 deg | 16.6% | 2.14 m/s | 7.7 |
| 15 deg | 26.8% | 1.35 m/s | 4.9 |
| 20 deg | 36.4% | 1.02 m/s | 3.7 |
| 30 deg | 57.7% | 0.70 m/s | 2.5 |
| 35 deg | 70.0% | 0.61 m/s | 2.2 |
| 39.2 deg | 81.7% | 0.55 m/s | 2.0 |
Computed from the formulas above. Not measured data.
Look at the 30-degree row. A climber gaining 0.35 meters per second there moves along the slope at about 0.70 m/s. That sits right on the lab’s walking-wins line.
What the steep-climb studies reported
A vertical kilometer race (VK) climbs 1,000 meters over a short, steep course. It has produced the best data on this question.
Giovanelli’s 2016 study had 15 mountain runners walk and run at seven angles from 9.4 to 39.2 degrees. The cost of each vertical meter was reported as similar from about 20 to 35 degrees. That’s roughly 36% to 70% grade. In short: past about 20 degrees, steeper isn’t cheaper, and it isn’t much dearer either.
Ortiz’s 2017 study, with 11 runners at 30 degrees, found cost rose in a straight line with speed. Walking won below 0.7 m/s. Running looked cheaper at faster speeds, from the authors’ extrapolation. Small lab samples like this make it a guide, not a rule.
Real races show the same pattern. In a 4.64 km VK with 835 meters of gain, 15 trained runners averaged 1.00 m/s on 20-degree sections early on. Later they slowed to 0.73 m/s. Their energy cost per meter rose from 17.4 to 23.4 joules per kilogram, about 35% more. The authors noted that runners below roughly 0.8 m/s may have switched to walking.
Translation: when you tire, the same hill costs more. Running it gets worse faster than walking it.
Your body switches early, and that’s okay
One 2020 preprint reported that runners switch between walking and running at a slower speed than the energy math says is best, on gentle grades. The two lined up near 15 degrees. It’s an early finding, so don’t build your race plan on it.
The practical lesson fits what coaches see. Your gut sense of “I should hike now” isn’t a perfect energy meter. It’s a decent start. Test it.
What ultra field data shows
In a 173 km race with about 3,000 meters of gain, 15 runners lost speed from start to finish. Level ground dropped 4.35 km/h. Downhill dropped 4.36. Uphill dropped only 2.26.
Uphill is where most people hike. It’s also where pace held up best. Hiking is a steady gear.
Fatigue favors it too. In the Tor des Geants (330 km, +24,000 m), 19 finishers were tested before and after. Their energy cost walking at +20% fell 11.5% after the race. Running at +15% fell 7.2%. In short: after days on your feet, walking gets relatively cheaper. The study didn’t find a crossover grade, so don’t read one into it.
Poles: faster, not cheaper
Poles didn’t lower the energy cost of steep uphill walking at submaximal effort in Giovanelli’s work. They cut the force through your feet and made all-out climbs about 2.5% faster. That was roughly 30 seconds on a 1.3 km, 433 m climb. In short: poles save your legs, not your fuel.
How to find your own switch point
Here’s a stylized example. Take a runner I’ll call Dana, 41, training for a 50-miler with 2,400 meters of gain. Her local hill runs about 12% for 20 minutes. She tried it twice at the same heart rate. Running, she covered about 3.9 km/h. Hiking, she covered about 4.3. The hike was faster at the same effort.
That told her something her race plan never had. On that hill, she should hike from the start.
Try it. Pick a climb of 8% to 15% and one of 20% or more. Hold the same effort on each. Note your pace running, then hiking. Do it fresh, and again late in a long run. If hiking matches your running speed, hike. You’ll bank energy for the flats.
Keep this honest. The studies used 10 to 19 well-trained runners, mostly men. Your number may differ.
Putting it into your training
AthleteOS doesn’t calculate a personal crossover gradient for you. It does the parts around it. Your AI coach builds a training plan from your goal race and adapts it when life gets in the way. Workout import brings in sessions from Garmin and Apple devices. Session analysis helps you review climbs afterward. Your fitness, fatigue and form scores show whether your hill days are building you or burying you.
Use that to schedule climbing days well. For the base work behind them, read how Zone 2 builds the aerobic base. For long run planning, see how to periodize an ultramarathon build and what pace your long runs should be. If you also race on the road, try how to run a sub-3 marathon. Ready to build your own plan? Start your 14-day trial.
Hike early. Hike on purpose.