Appliances & Utilities calculator
What Water Filter Size Do I Need?
Use peak required water flow, daily filtered volume, desired days between cartridge changes to find water-filter minimum flow and cartridge capacity.
Enter your measurements
What Water Filter Size Do I Need uses peak required water flow, daily filtered volume, desired days between cartridge changes and the other configured measurements to return water-filter minimum flow and cartridge capacity with a formula written specifically for this tool.
- Peak required water flow — Required
- Daily filtered volume — Required
- Desired days between cartridge changes — Required
Water-filter minimum flow and cartridge capacity
Enter the measurements above to calculate water-filter minimum flow and cartridge capacity.
How the calculation works
V12 calculation: minimumRatedFlow=peakFlow; minimumCartridgeCapacity=dailyVolume×replacementDays. This is the implementation specification for this calculator.
Worked example
Example: Peak required water flow = 0.5 L/s; Daily filtered volume = 4 L; Desired days between cartridge changes = 30. Result: Minimum Cartridge Capacity = 120 L; Minimum Rated Flow = 0.5 L/s.
Before you decide
Recheck the limiting measurement before purchase or installation. This page calculates the stated geometry or quantity only; product-specific construction or installation details can still affect the final choice. For what water filter size do i need, the limiting result on this page is water-filter flow and cartridge capacity.
Direct measurement/geometry calculation. No external reference is required for the arithmetic itself; the result is derived only from the user-entered measurements and the formula stored in calculationLogicJson.
Frequently asked questions
What does the Water Filter Size calculator tell me?
It returns water-filter flow and cartridge capacity from the measurements entered on this page. The calculation is specific to water filter size, so the result should be compared with the exact product or specification you are considering.
Which measurements should I take for water filter size?
Measure peak required water flow, daily filtered volume, desired days between cartridge changes. Use clear, usable dimensions rather than nominal room or product labels.
Should I round the water-filter flow and cartridge capacity?
Keep the calculated value for comparison, then choose a real product that meets or stays within the returned water-filter flow and cartridge capacity while allowing for the clearances, tolerances or ratings shown by its manufacturer.