Two hikes, both 9 miles. One is a lazy riverside loop. The other is Old Rag in Virginia, which climbs about 2,400 feet and makes grown adults question their choices at the rock scramble. Distance told you nothing there. Elevation gain told you everything.

So how do you actually get that number before you’re standing under it? Three ways, from easiest to most old-school.

Way 1: Draw the route and let the terrain data answer

The fastest method: trace your route on our route planner. Turn on Snap to trails, click the trailhead and the summit, and the line follows the real path while the planner reads elevation along it and adds up every climb.

One thing worth knowing about what “adds up” means. Trails roll — up 40 feet, down 20, up 60. Gain counts only the ups, and good tools ignore tiny wobbles in the data so the total doesn’t get inflated by noise. Ours skips anything under 5 meters, which is the same trick GPS apps use on their recordings. That’s why an honest tool says 2,400 feet where a sloppy one bragged 3,100.

Way 2: Take it from a guidebook or GPX — but know why numbers disagree

Guidebooks, park signs, and downloaded GPX tracks all publish gain figures, and they rarely match each other. Old Rag shows up as anything from 2,200 to 2,600 feet depending on where you look.

Nobody’s lying. They’re measuring differently — different filters for that up-40-down-20 rolling, different terrain data, slightly different trailheads. Differences of 10–20% between sources are normal, not a red flag. Pick one number, know it’s an estimate, and plan with margin. If a source is way outside that band, trust it less.

Way 3: Count contour lines like it’s 1985

No signal, paper map? Still works. On a USGS topo map, elevation lines come at fixed steps — often 40 feet apart. Find your route, count the lines it crosses going uphill, multiply. Cross 55 lines climbing at 40-foot intervals and you’re looking at about 2,200 feet of gain.

It’s rough. It misses the small rollers entirely. But it’s the method that keeps working when your battery doesn’t, and every hiker should have done it at least once — it teaches you to see steepness on a map instead of trusting a number you didn’t check.

Why the number matters this much

Because climbing is what costs you. The rule mountain clubs have used since 1892 — Naismith’s — says every 2,000 feet of gain adds a full hour to your hike, on top of the distance math. Old Rag’s 2,400 feet is over an hour of pure climbing tax.

Feed your gain figure into the hiking time calculator and that tax gets computed for your fitness and terrain, not a textbook hiker’s. The route planner does it automatically if you drew the route there.

The honest part

Every method above gives an estimate. Terrain data smooths over boulders, guidebooks disagree, contour counting misses the rollers. Don’t chase the “true” number — it doesn’t exist at the precision people argue about. What exists is the difference between knowing roughly what a climb demands and finding out at the bottom of it.

Get the number. Add margin. Then go meet the hill it describes.