Six free water calculators in one place. Work out your daily intake, estimate your body water percentage, check what your tap water actually contains, price a softener before anyone quotes you, convert water volume to weight, or find a refill station near you. No signup, no email, no ads in the way.
Free, instant, accurate. Built around the questions our readers actually ask.
Get your personal daily water target based on weight, activity, and climate. The US National Academies put total daily fluid at about 3.7 litres for men and 2.7 litres for women, but the "8 glasses a day" rule is too generic — this isn't.
Estimate your body water percentage using the Watson formula — the same one used in clinical research. Adults typically sit around 50–65% for men and 45–60% for women.
See what has been reported in your local supply, from PFAS and lead to hardness, and what each result means. Being under the EPA limit is not the same as being absent.
Get realistic install and running costs before any salesman quotes you. Most homeowners land between $500 and $2,000 for the unit, plus roughly $50–$150 a year in salt.
Gallons, liters, ounces, kilos — every unit you'd ever convert. Handles US vs UK gallons properly. Perfect for cooking and aquariums.
Find SodaStream CO₂ exchanges and 5-gallon water refill stations near you. Live retailer prices and locations, by ZIP code.
Every tool here uses peer-reviewed formulas, official guidelines, or tested data. Not marketing math.
Watson formula for body water, IOM hydration guidelines for daily intake — published, tested, used by clinicians.
Water quality thresholds match EPA Safe Drinking Water Act standards. No invented "ideal" numbers.
Cost estimators use current US/UK retail pricing — refreshed monthly so quotes don't go stale.
Nothing is stored on our servers. No accounts, no tracking pixels, no email harvesting. Calculate & close.
Reader favourites
Chosen on certification and tested performance — not on price.
AquaTru Countertop RO
Removes 84 contaminants. No plumbing.
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Best budget pick
Brita Elite 10-Cup Pitcher
Reduces 99% lead. Filter lasts 6 months.
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Best shower filter
AquaHomeGroup 20-Stage
KDF-55 + calcium sulfite. Spare included.
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Best for hard water
Aquasana SimplySoft 40K
NSF/ANSI 44 certified. Stops scale.
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