Trail grade — percent, degrees, and what your legs actually feel
I once picked a trail off a map because the description said '2 miles, moderate'. The 'moderate' was a 22% average grade. I remember stopping every hundred feet and thinking about my life choices.
Trail grade is quoted as a percentage: rise divided by horizontal run, times 100. A 10% grade climbs 10 feet vertically for every 100 feet horizontally. A 20% grade climbs 20 feet for every 100. These numbers look small next to percentages you're used to (30% off at a store, 100% humidity) and they read as gentle. They aren't.
The equivalent in degrees is smaller still. 10% = 5.7°, 15% = 8.5°, 20% = 11.3°, 30% = 16.7°, 45° = 100% (rise equals run). A 45° slope, which most people would call 'a cliff you can just barely walk up', is a 100% grade. Above 45° / 100% you're into scrambling territory.
What each grade feels like on foot
0-5% (0-2.9°): Flat by hiker standards. A rail-to-trail path. You can chat.
5-10% (2.9-5.7°): Gentle climb. Steady breathing. Most well-graded American backcountry trails try to average here.
10-15% (5.7-8.5°): You notice. Conversation is harder. A day of this is real work.
15-20% (8.5-11.3°): Sustained here is where trekking poles start earning their weight. Common on European alpine trails, which don't switchback as aggressively as US trails.
20-30% (11.3-16.7°): Steep. You're pushing off knees on the way up. Coming down is worse than going up.
30-45% (16.7-24°): This is where 'trail' becomes 'route'. Scrambling with hands. Not sustainable for long stretches.
45%+ (>24°): Effectively climbing.
Roads and railways
Roads are graded gentler than trails because vehicles are less efficient at climbing than legs. The steepest US interstate grades are around 6% (Colorado's Eisenhower Tunnel approach), and truck warning signs typically appear at 5%. San Francisco's famous Filbert Street is 31.5%, which is genuinely alarming to drive.
Standard-gauge railways top out around 2.5-4% for main lines because steel wheels on steel rails lose traction quickly on grades. Rack railways (cog railways) with a toothed center rail can climb 25%+ but are slow and expensive to build.
Wheelchair ramps under the ADA are capped at 8.33% (1:12) with landings every 30 feet. Any steeper and it's not a ramp, it's a lawsuit.
How to eyeball it
A 10% grade looks flat from a distance and 'noticeable' up close. A 20% grade looks like 'a hill'. A 30% grade looks like 'a steep hill'. A 45° / 100% grade looks like a wall and you'd never call it a hill. Trust the number more than your eye — perspective on distant slopes is systematically deceiving, and photos flatten grades dramatically. That gentle-looking trail in the photo is probably 15%.
Try the converters mentioned in this article
FAQ
Why is downhill often harder than uphill?+
Eccentric muscle contractions (lengthening under load) cause more damage than concentric ones. Uphill burns lungs; downhill destroys quads and knees. That's why long descents leave you sorer for longer.
What's Naismith's rule?+
A hiking time estimate: 1 hour per 5 km horizontal plus 1 hour per 600m of ascent. Reasonable for fit hikers on decent trails. Add substantial time for steep, rough, or wet ground.
This article was written by The Turbo Unit Converter engineering desk (Applied metrology & engineering units) and last reviewed on 2026-07-22 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.