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Pool Calcium Hardness Calculator

Reviewed 2026-04

Find out how much calcium chloride your pool needs to hit the ideal 200–400 ppm range. Includes a staged dosing plan so you avoid calcium scaling on your equipment.

Built on CDC and ANSI pool-water standards

The 300 ppm starting value is an example. Establish your target for the finish and measured water balance; this calculator only converts that chosen increase to a dose.

Don't know? Try:

Use the target from your surface/equipment instructions or a qualified water-balance assessment.

Read this off your bag. Pool-grade calcium chloride is commonly 94%, but 77% flake is also sold and needs about 22% more product for the same result.

Confirm your inputs

Examples remain unconfirmed until you check each value. Confirm fresh test results and your measured pool volume before using a dose. Editing a value clears its confirmation.

Popular calcium chloride

Enter your pool data above for personalized quantities

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In The Swim

Calcium Hardness Increaser · 25 lb bag

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Frequently asked questions

What calcium hardness target should I use?

Choose a target from the surface/equipment instructions or a qualified water-balance assessment. This tool requires that choice and calculates the mass to reach it. It does not assign every pool a 200–400 ppm target. A balance assessment needs pH, carbonate alkalinity, CH, water temperature and dissolved solids.

Does calcium hardness predict metal corrosion?

No. LSI describes calcium-carbonate saturation, not metal corrosion. Undersaturation can etch cementitious surfaces; supersaturation can cause scale. Hardness alone cannot establish either condition. Vinyl and fiberglass do not establish a universal calcium minimum for protecting metal equipment.

How do I raise calcium hardness?

Use pool calcium chloride with the selected ingredient purity. The first estimated addition raises CH by no more than 50 ppm, a conservative staging choice. Follow the exact label for mixing and application; dissolving calcium chloride releases heat. Retest after at least 24 hours, or the longer label interval, and recalculate from the new reading before adding more.

How do I lower hardness?

First confirm the reading and assess full water balance. Exchange with lower-hardness water may help, but the required exchange is not permission to drain. Obtain a construction and groundwater assessment and a suitable professional exchange plan before substantial lowering.

When should I test CH?

Check at opening and regularly during operation, after water replacement, calcium-containing chemicals, or observed scale/etching. Follow surface and equipment requirements. Test after the prescribed mixing interval before a follow-up calcium addition.

Alkalinity Calculator →pH Calculator →

How we calculate this
Our formulas follow ANSI pool-water standards and are validated against CDC pool-water health code guidelines. We show you the math so you can verify every result. Questions or corrections? Please contact us.