Calculator
Formula Used
This calculator estimates regeneration salt use from hardness and wash volume. Hardness is converted to ppm as CaCO3, then scaled by a stoichiometric mass ratio and practical adjustment factors.
- hardness_ppm = input ppm, or °dH × 17.848
- salt_g_per_cycle ≈ hardness_ppm × water_L × 1.168 / 1000 × setting × season ÷ (efficiency/100)
- Reservoir usable salt = capacity_kg × 1000 × purity%
- Days between refills = usable_salt_g ÷ (salt_g_per_cycle × cycles_per_week/7)
Tip: If your dishwasher has a hardness dial, the setting factor can reflect that calibration.
How to Use
- Test your water hardness or read a utility report.
- Enter your average cycles per week and water per cycle.
- Keep setting factor at 1.0, then fine-tune if needed.
- Add reservoir size and salt purity to estimate refill timing.
- Optionally enter price per kg to estimate monthly cost.
- Press Calculate to see usage totals and refill interval.
Example Data Table
| Hardness (ppm) | Water per cycle (L) | Cycles/week | Reservoir (kg) | Salt per cycle (g) | Days between refills |
|---|---|---|---|---|---|
| 120 | 10 | 7 | 1.2 | 1.65 | ~104 |
| 250 | 12 | 10 | 1.2 | 4.12 | ~50 |
| 400 | 14 | 14 | 1.5 | 7.70 | ~19 |
Values are illustrative and assume setting factor 1.0, season 1.0, efficiency 85%, and purity 99%.