Pool Salt Calculator: Pounds of Salt to Add
Find out exactly how many pounds of pool salt to add to reach your target salinity — enter your pool volume plus the current and target ppm for an instant, formula-based answer.
Calculator
Add 266.9 lb of pool salt to raise 10,000 gallons from 0 to 3,200 ppm.
A salt-chlorine generator makes its own chlorine by passing pool water over a charged cell that converts dissolved salt into hypochlorous acid. For the cell to work, the water has to sit in a fairly narrow salinity band — most systems ask for roughly 3,200 ppm (parts per million), though the exact target is printed on your cell. This calculator tells you how much salt to pour in to get there.
Because salt is a dissolved solid that does not evaporate or break down, the amount you add depends only on two things: how much water you have and how far the salinity has to climb. That makes the math exact and permanent — the number you get today is the same number you would get in ten years for the same pool.
Formula
Salt is a solute, so the weight to add scales with the pool volume and the rise in concentration you want:
salt (lb) = gallons × (target ppm − current ppm) × 0.00000834
- gallons — total water volume of the pool.
- target ppm − current ppm — the salinity gap you need to close.
- 0.00000834 — the solute constant: 8.34 lb (the weight of one US gallon of water) ÷ 1,000,000, because ppm is roughly milligrams of salt per liter, i.e. parts per million by weight.
If the current salinity already meets or exceeds the target, no salt is needed; to lower salinity you dilute by draining and refilling (see the Salinity tool).
Worked example
Take a fresh 10,000-gallon pool at 0 ppm that you want at 3,200 ppm:
10,000 × (3,200 − 0) × 0.00000834 = 266.9 lb
That is about 6.7 × 40-lb bags. Because salt dissolves slowly, add about three-quarters of the estimate first, brush it across the floor to help it dissolve, run the pump for 24 hours, then re-test and top up the rest. As a handy rule of thumb, raising a 10,000-gallon pool by 1,000 ppm takes 83.4 lb of salt.
Adding salt the right way
Use salt sold for pool use (sodium chloride, at least 99% pure, non-iodized and free of anti-caking or yellow-prussiate additives). Pool salt, water-softener salt and food salt are chemically the same NaCl, but the purity grade matters for a clean cell.
Never dump salt directly on the cell or into the skimmer. Broadcast it slowly across the deep end with the pump running and the generator switched off until the salt has fully dissolved — usually within 24 hours. Undissolved salt piled on a vinyl or fiberglass floor can stain or bleach it, so brush any mounds until they clear.
Test again after a full turnover. Your cell displays an instantaneous reading, but a drop-based test kit or a lab strip confirms it. Salt is only lost through splash-out, backwashing, draining, and leaks — not through evaporation or normal chlorination — so once you hit the target you usually only top up a little each season. If you overshoot, the only way down is dilution: drain some water and refill.
Cold water reads lower on many cells, so a pool that shows a slightly low number on a chilly morning may be fine once it warms up. When in doubt, trust a manual test over the cell and stay within the range your manufacturer prints on the unit.
Reference table
Pounds of pool salt for two common jobs, by pool size (uses the same 8.34e-6 lb/ppm/gal constant as the calculator above):
| Pool volume | Fresh → 3,200 ppm | Per +1,000 ppm |
|---|---|---|
| 5,000 gal | 133 lb | 41.7 lb |
| 10,000 gal | 267 lb | 83.4 lb |
| 15,000 gal | 400 lb | 125.1 lb |
| 20,000 gal | 534 lb | 166.8 lb |
| 25,000 gal | 667 lb | 208.5 lb |
| 30,000 gal | 801 lb | 250.2 lb |
Round to whole bags and add in stages, re-testing between doses.
Frequently asked questions
How much salt do I add to a 15,000-gallon pool?
To bring a fresh 15,000-gallon pool from 0 to 3,200 ppm you need about 400 lb of salt (15,000 × 3,200 × 0.00000834 = 400.3 lb), or roughly ten 40-lb bags. If the pool already holds some salt, enter the current ppm above so the tool only counts the gap you still have to close.
What ppm should a saltwater pool be?
Most residential salt-chlorine generators are designed for about 2,700–3,400 ppm, with 3,200 ppm a common midpoint. The exact figure is printed on the cell — always match your unit rather than a generic number, because a low level starves the cell and a high level can trigger a shut-off or corrode fittings.
How many 40-lb bags of salt is that?
Divide the pounds by 40. For example, 266.9 lb ÷ 40 ≈ 6.7 bags, so you would buy seven bags and hold back part of the last one until you have re-tested. It is always safer to under-dose and add more than to overshoot, since the only way to lower salt is to drain and refill.
What kind of salt should I use?
Use pool-grade sodium chloride that is at least 99% pure, non-iodized and free of anti-caking agents. Solar or evaporated salt sold in 40-lb bags for pools or water softeners works well. Avoid rock salt with visible impurities and any salt containing yellow prussiate of soda, which can stain the finish.
How long before I can test after adding salt?
Give the pool a full turnover with the pump running — usually 24 hours — so the salt fully dissolves and mixes before you trust a reading. Brush any undissolved salt off the floor to speed things up and prevent staining.
Do I lose salt over time?
Not through evaporation or chlorination. Salt only leaves the pool with water that leaves it — splash-out, backwashing, draining after heavy rain, or a leak. That is why you usually only top up a modest amount at the start of each season rather than dosing continuously.