The Pool Calculator

The Pool Calculator takes care of all the math that might come up while you are keeping your swimming pool's water chemistry in balance, telling you exactly how much of each chemical to add. For background on what the various numbers mean, see Basic Pool Chemistry. If you have comments or questions about The Pool Calculator please write to jason@poolcalculator.com. For help with your pool try Trouble Free Pool, a swimming pool and spa care forum.

You are welcome to use The Pool Calculator on the web for free. If you find The Pool Calculator to be of value please consider a donation to help support my development and web hosting expenses.

	Now	Target		Units
Size			Mouse over a field for detail
FC	Goal: Not Setup		Add of % bleach. Jug size . or add by weight or by volume of . Note: Dichlor and trichlor add CYA and lower pH. Cal-hypo adds CH.

pH	Goal: Not Setup		Given TA of and Borate of : Add by weight or by volume of washing soda or soda ash or add by weight or by volume of borax. Add of muriatic acid or add by weight or by volume of dry acid. Note: pH calculations depend on TA and Borate. Results are approximate and can be off significantly for large pH changes. Changing your pH will also change your TA.

TA	Goal: Not Setup		Add by weight or by volume of baking soda. To lower TA you reduce pH to 7.0-7.2 with acid and then aerate to increase pH. Note: Adding baking soda will also raise your pH.

CH	Goal: Not Setup		Add by weight or by volume of calcium chloride or add by weight or by volume of calcium chloride dihydrate. To lower CH you replace of the water with new water, with CH of .

CYA	Goal: Not Setup		Add by weight or by volume of stabilizer or add of liquid stabilizer. To lower CYA you replace of the water with new water. Note: It can take solid stabilizer up to a week to dissolve. It will also lower your pH.

Salt			Add of salt. To lower Salt you replace of the water with new water.
Borate			Add by weight or by volume of and of 31.45% muriatic acid to compensate for the pH increase. To lower Borate you replace of the water with new water. Note: The pH should be tested and adjusted as needed after increasing the borate level.
Temp			Mouse over a field for detail
CSI			Calcite Saturation Index - requires pH, TA, CH, CYA, Temp, uses Borate, Salt Less than -0.6 is suggestive of problems for plaster, tile, stone, and pebble pools. Greater than 0.6 is suggestive of problems for all pools.
Suggested FC Levels			SWG: Normal: to Shock: Mustard Algae Shock: Suggested target FC levels based on the current CYA level for outdoor pools. Note: Be careful if your CYA is really and truly zero!
Suggested Goal Levels			Use suggested goal levels from: Primary source of chlorine: Pool surface: Note: Suggested goals are simply a starting point. There are many situations that are not covered by these basic guidelines.

Notes
Unless you are shocking your pool, it is always best to add less than the full amount, wait a little while to allow the addition to mix thoroughly, and then retest to see where you are. Also, keep in mind that the volume of powders can vary from manufacturer to manufacturer.

Estimating pool volume
A wide by long by deep pool holds .
If the depth varies, use the average depth of the pool. A good approximation is the shallow end depth plus the deep end depth divided by two. Irregularly shaped pools can be approximated by estimating the average length and width and using rectangular.

Effects of adding chemicals
Adding of will
Note: pH calculations are not exact. These numbers are only suggestive of the relative magnitude of the pH change you can expect. Small changes, +-0.4, with pH between 7.2-7.8, TA around 80-120, and Borate near zero will be approximately correct. The further you go from those ranges the less these pH changes will correspond to reality.