Hiking Water Calculator

How the water estimate is built

No single number fits every hiker. Sweat rate depends on heat, effort, body size, altitude and pace. This calculator starts from a common planning baseline of about 16 fluid ounces per hour, roughly half a liter, for moderate hiking in mild weather. It then scales that figure by temperature, effort and pack weight, and adds a margin so you finish with some left.

Temperature adds 2 percent to your rate for each degree above 70 F and removes 2 percent for each degree below, within limits. Effort multiplies the rate by 0.75 for easy walking or 1.4 for steep climbing. Pack weight above 15 pounds adds 1 percent per pound. These factors are simple planning multipliers and editable example defaults, not lab values, so adjust them after you learn your own pace.

Take the default: 75 F, six hours, moderate effort and a 20-pound pack. The rate is 16 x 1.10 x 1.0 x 1.05, or about 18.5 ounces per hour. Over six hours that is 111 ounces, and a 15 percent margin brings it to about 128 ounces, or 4 quarts. That much water weighs roughly 8.3 pounds, which is a big share of your load and a good reason to know where you can refill.

Plan refills when you can. If a route has reliable streams, carry less and treat what you collect. On dry routes, carry the full amount plus a reserve. Hot days at elevation can raise needs well above this estimate. For a whole trip, pair the result with the camping food and water calculator and check the pack weight calculator to see what the water does to your load. Calorie questions go to AthleteCalcs, our sister site. Keep a note of how much you actually drank on each hike so the next estimate starts from your own numbers rather than a general rule.

Where these numbers come from

The formulas and default values in this calculator are based on:

• Adventure Calcs planning model built on the widely used rule of thumb of about half a liter (16 fl oz) per hour for moderate hiking
• water weight of 8.34 lb per gallon. Note: temperature, effort and pack multipliers are editable example factors, not measured values

This is a planning estimate, not medical, legal or immigration advice. Fees, allowances, limits and entry rules change, so confirm the figures with your airline, cruise line, customs agency or the official government source before you book or travel, and follow their rules if they differ from this page.