Revised planning calculator
Pool Calcium Hardness Calculator
Calcium hardness increase with the selected 77% or 94% CaCl2-equivalent product. This does not evaluate saturation balance or choose a target for your surface.
Enter your measured values
Calcium hardness increase with the selected 77% or 94% CaCl2-equivalent product. This does not evaluate saturation balance or choose a target for your surface.
Use decimals, simple fractions such as 1/4, or grouped commas such as 10,000. Blank or invalid values never become defaults.
Method, supported products, and references
Concentration is approximated as mg/L. US gallons × 3.785411784 × selected ppm increase / 1000 gives grams of the measured constituent. Alkalinity and hardness use calcium-carbonate-equivalent conversion, then divide by the selected product assay. Ounces and pounds are weight units, never fluid volume.
Solid product with a label assay of 77% anhydrous CaCl2 equivalent by weight. The assay already accounts for hydration; no second hydration correction is applied.
Solid product with a label assay of 94% anhydrous CaCl2 equivalent by weight. The assay already accounts for hydration; no second hydration correction is applied.
Testing and measurement
Start with reliable information
Use a calcium hardness drop test. Strips can miss the difference between safe and scale-prone water.
Keep the product label available, never mix pool chemicals together, and ask a qualified pool professional if you are unsure how to interpret a reading.
Companion Guide
Why Calcium Hardness Matters More Than You Think
The companion guide remains available for background reading. Its examples are not a personalized dose or a substitute for product instructions.
Read the guide