Do the walk-out math at the trailhead, not at mile six

Quick answer: Figure three miles an hour on a flat trail. Add one hour for every 2,000 feet you climb. Cut your speed in half off trail, with a heavy pack, or with an injury. Set a turnaround time before you leave the truck.

You're sitting on a rock with a swollen ankle. The sun is behind the ridge. You think the truck is about three miles back, and you think you can make it by dark.

You're probably wrong on both counts. Tired, hurt, hungry people guess short on distance and fast on speed. Every time. The fix isn't better instincts. It's doing the arithmetic while you're rested and the coffee's still warm.

Three numbers that do most of the work

The old rule is Naismith's, and it's been used by hill walkers for well over a century. One hour for every three miles. One extra hour for every 2,000 feet of climbing.

Run it on a real trip. Four miles with 1,500 feet of gain is 80 minutes of walking plus 45 minutes of climbing. Call it two hours and five minutes, one way, at an easy pace, with no stops.

That's the best case. Here's how it falls apart:

• Off trail: brush, deadfall and creek crossings can drop you to one mile an hour or less.
• A heavy pack: slower uphill, and much slower on a steep descent, where your knees take the load.
• Injury: halve your speed as a starting guess, then plan for worse.
• Fatigue: the last third of any trip runs slower than the first. Your math should know that.

Downhill isn't free either. A steep, loose descent on a bad ankle can take as long as the climb did.

Learn your own pace

The formula gives you a starting point. Your legs give you the real number.

Find a quarter-mile track and walk four laps at your normal hiking pace. Time it. Then do it again wearing the pack you'd actually carry, loaded. The gap between those two times is your pack penalty. Most people have never measured it.

Next, count your paces. Every time your right foot lands, that's one count. Over 100 yards on flat ground, most adults land somewhere near 60, but measure yours instead of trusting that number. It climbs on hills and in soft ground.

Ranger beads are the cheap tool for this. They run about $10, or you can knot a piece of paracord for nothing. Slide one bead every 100 yards and you'll know how far you've gone without looking at a screen. They won't be perfect. They'll be closer than your gut.

Read distance off the map

A standard USGS 7.5-minute topo map is 1:24,000. One inch on paper is 2,000 feet on the ground, so a mile is about 2.6 inches. The ruler edge on a baseplate compass makes this quick. Suunto and Silva both make good ones, and $20 to $40 buys a solid one.

Trails don't run straight, so lay a piece of string along the route, switchbacks included, then stretch it against the scale. A ruler across the corners will flatter you.

Then count contour lines. Many maps use 40-foot intervals, though yours may differ, so check the legend. Twelve lines crossed is about 480 feet of gain. Plug that into the formula.

Your phone is a fine tool, and a poor only tool. Download offline maps before you leave the house, since the signal won't be there. Put it in airplane mode to save battery and carry a $20 to $30 power bank. Keep a printed map in a zip bag as your backup. A paper map doesn't run out of charge or crack when it hits a rock.

Do the daylight math

Look up sunset before you go. Then check it against the sky.

Hold your arm out flat with your fingers together, and stack your hand between the sun and the horizon. Each finger is roughly 15 minutes, so a four-finger hand is about an hour. It's rough and it varies with latitude, but it beats guessing. Try it on a clear evening at home so you trust it in the field.

Add a headlamp to the pack, $25 to $40 for a good one, plus spare batteries. A light doesn't make night travel smart. It makes the first hour of dusk usable and gives you something to work with if you stay put.

Know this rule cold: if the math says you can't reach the truck or a known trail junction before dark, the answer is usually to stop, get warm, and stay visible. Walking off-trail in the dark is how a bad afternoon becomes a rescue. Our piece on what to do in the first hour you're lost in the woods covers that decision in detail.

Set the turnaround before you set out

The summit, the lake, the next ridge. Everyone wants to push for it. So decide ahead of time, in writing, when you turn around no matter what.

Pick a clock time, not a place. "We turn around at 1:00" works. "We turn around when we get tired" doesn't, because tired people are terrible judges of tired.

A good rule is to turn back when half your usable daylight is gone, or when the return math (using your slow numbers, not your best ones) leaves you less than an hour of margin before sunset.

Then tell someone. Leave a note with a person you trust: the trailhead, your route, your vehicle, the time you'll be back, and the time they should call for help if you aren't. Make that second time generous but firm. A plan nobody knows about is only a hope.

If you carry in the backcountry

Lawful carry in the woods is a right, and it comes with responsibilities that start well before the trail. Rules for carrying on public land, in parks, in vehicles, and across state lines vary by state, province and city, sometimes by the specific property. Check local law before you go. Nothing here's legal advice, so ask a qualified attorney or instructor if you're unsure. Our piece on what your carry permit actually does at the state line is a good place to start.

Two practical points for this subject. First, a handgun, holster and spare ammunition add a few pounds, and that weight belongs in your pace math. Second, the four rules of firearm safety apply at camp, in the truck and on the trail exactly as they do at the range. Treat every gun as loaded. Keep your muzzle pointed somewhere safe. Keep your finger off the trigger until you're ready to fire. Know your target and what's beyond it.

Trailhead lots are an easy spot for a break-in, since everyone parked there's gone for hours. If you aren't carrying a firearm on your person, don't leave it loose in the cabin of the truck. Where the law allows it, lock it up out of sight. At home, keep it locked away from children. If you've never had formal instruction, start with a class from a qualified instructor. Your first firearms class isn't a test you can fail, and it's money well spent.

The same goes for navigation. A land navigation course from a qualified instructor is worth a weekend. Reading about a compass is one thing, and taking a bearing in a drizzle with cold hands is another. Check with your local outdoors club or a certified instructor and put it on the calendar.

Do it at the truck

Before you shoulder the pack, do the math out loud. Distance, climb, your slow pace, sunset, turnaround time. Write the numbers on a card and put it in your pocket.

At the trailhead the number will look comfortable. At mile six, it won't. That's why you do it now.