Ultralight backpacking calculators

The numbers on this site all hang off one definition. Base weight is everything in or on your pack minus food, water and fuel. The pack itself counts. Clothing you are wearing at the trailhead does not, and neither do your trekking poles while they are in your hands. That single convention is what lets two hikers compare gear lists at all, and it is why the base weight calculator is the one to start with.

From there the tools chain. Base weight decides how much pack you need, which the pack volume calculator turns into litres. Food and water are the consumables that base weight deliberately excludes, and they are usually the heaviest things you carry: the food weight calculator and the water carry calculator put real figures on both. The pack weight to body weight calculator then checks the loaded total against the guidance most people have heard quoted, and the sleep system temp calculator checks the one system where being wrong is genuinely dangerous.

If you want the itemised version rather than eight summary boxes, the gear list builder takes individual items, rolls them into the same buckets, and shows the weight bars per category as you type.

What these calculators will not do

They will not tell you what is safe. A calculator can tell you that a 20 degree quilt over an R 2 pad is thermally mismatched, and it can tell you that four litres of water weighs 8.8 pounds. It cannot know that the spring you planned around went dry, or that the forecast low was measured at a valley weather station 3,000 feet below where you intend to sleep.

Two specific warnings run through every relevant page here. Sleeping bag and quilt temperature ratings are survival ratings, not comfort ratings, and the comfort figure usually sits 10 to 15 degrees Fahrenheit warmer than the EN or ISO limit number. Hollow fibre water filters are destroyed by a single freeze with no visible damage, and they remove bacteria and protozoa but not viruses. Neither fact shows up in a weight column, and both have ended trips.

Going ultralight must not mean going unprepared. Cutting weight is a design exercise, not a subtraction exercise, and rain gear, insulation, navigation, water treatment and an emergency communication plan are fixed costs rather than places to save grams. Every tool here is built to help you carry less of what you do not need, not less than you need.

Each tool exists because one specific question comes up constantly and gets answered badly. The table below maps the question to the tool and to the figure the tool is built around, so you can go straight to the one you need rather than opening all six.

The four numbers that settle most gear arguments

Before you open any of them, these four constants resolve a surprising share of the disagreements people have about gear lists, and none of them require a calculator at all.

Water weighs 2.2 lb per litre. A decision to carry four litres instead of two costs 4.4 lb, which is more than most people save by replacing an entire shelter. That one fact reorders almost every ultralight priority list, and it is why the desert kit spends its ounces on capacity and shade rather than on grams of gear.

Food runs about 1.5 lb per day in three season conditions and closer to 2 lb per day in winter, when staying warm overnight burns through reserves a summer trip never touches. A five day carry is therefore 7 lb 8 oz on day one, which is more than the entire base weight of a super ultralight kit. Calorie density, not menu preference, is the lever: 110 calories per ounce is realistic for a mixed resupply, and the calories per ounce chart shows what moves it.

The Big Three are roughly 55 percent of base weight at every level. Shelter, sleep system and pack come to about 15 lb 8 oz in a traditional kit and about 4 lb 7 oz in an ultralight one, and that ratio does not improve as you get lighter. There is no point at which the small items become the main problem, which is why every weight cutting method starts in the same place. The Big Three guide takes it apart item by item.

A frameless pack carries well to about 25 lb total and badly above 30 lb. Total means base weight plus food, water and fuel, so a 14 lb base weight plus five days of food plus two litres of water is already past 25 lb before anything goes wrong. That is the entire reason the pack is bought last rather than first, and it is the single most expensive ordering mistake in this hobby.

What these tools deliberately do not do

They do not store anything. Every calculator here runs in your browser, and the numbers you type are never transmitted to us or saved anywhere. There is no account, no export wall and no email required, which also means we cannot recover a list you lose, so keep your own copy of anything that matters. The gear list builder works the same way and keeps your list in the page address, which is what lets you bookmark it or send it to a hiking partner.

They also do not make judgements. A calculator returns arithmetic on the numbers it is given. It does not know your fitness, your experience, the forecast, the snowpack, the water report, the fire restrictions or the permit conditions, and none of those can be inferred from a base weight. Use the output as an input to a decision, never as the decision. When the number and the conditions disagree, the conditions win.