Water Filter Life Expectancy Calculator
Calculate exactly when to replace your water filter based on local water hardness (TDS) and usage. Includes database of 40+ brands.
1. Select Your Filter Brand
2. Water Hardness
3. Household Usage
(Est. 0.5 gallons per person/day for drinking/cooking)About
Most water filters come with a generic lifespan rating like "lasts 2 months" or "good for 40 gallons." However, these ratings are based on standard laboratory water conditions. If you live in an area with hard water (High TDS), your filter's ion exchange resin works significantly harder, depleting its capacity much faster than the box suggests.
This calculator provides a realistic replacement schedule by adjusting the manufacturer's rated capacity against your household's specific water hardness and daily consumption. Replacing filters on time ensures you aren't drinking contaminants from a saturated filter or wasting money throwing away good cartridges.
Formulas
The effective capacity is inversely proportional to the Total Dissolved Solids (TDS) relative to the standard testing baseline (usually 100-150 PPM). The simplified formula for estimation is:
The remaining days are then calculated by:
Reference Data
| Water Hardness (TDS) | Classification | Filter Life Impact | Typical Regions |
|---|---|---|---|
| 0 - 50 ppm | Micro-filtered / Distilled | Extended Life (+20%) | Rare / Treated |
| 51 - 100 ppm | Soft Water | Rated Life (100%) | New England, PNW |
| 101 - 200 ppm | Moderately Hard | Reduced Life (80%) | Southeast US |
| 201 - 300 ppm | Hard | Significantly Reduced (60%) | Midwest, Texas |
| 301+ ppm | Very Hard | Half Life (50%) | Arizona, SoCal |