WATERFILTERLAB.COM
Calculators
Quick planning tools for water filters: replacement timing, cost per gallon, flow rate & fill time, and hard water conversions.
Planner
Replacement Planner
Estimate how often you’ll replace a cartridge using daily filtered water and filter capacity. Planning estimate only.
Estimated daily filtered water
— gal/day (≈ — L/day)
Estimated time to replacement
—
Estimated replacements per year
—
Real life varies with water quality (sediment, chlorine/chloramine), usage spikes, and flow preferences.
Maintenance & replacement guide →
Cost
Cost per Gallon Calculator
Estimate cost per gallon and monthly cost from filter price, capacity, and your daily use. Currency-agnostic: enter your local prices.
Cost per gallon
—
Estimated monthly cost
—
Estimated yearly cost
—
This covers cartridge cost only (not the housing, faucet, tank, or install parts).
More tools & calculators →
Flow
Flow & Fill Time
Convert flow rate and estimate how long it takes to fill a bottle/pitcher/container.
Flow conversion
—
Estimated fill time
—
If flow drops over time, it may be due to clogging/sediment or nearing replacement.
Contaminants & removal basics →
Hardness
Hard Water Converter
Convert hardness units and get a simple classification for planning. (Hardness alone doesn’t describe all water issues.)
Converted hardness
— ppm
(≈ — gpg)
Classification
—
Scale planning note
—
Hardness is mainly about calcium/magnesium. Taste/odor, chlorine, lead, PFAS, etc. are separate topics.
Water quality basics →