How to use the pool salt calculator
- Enter the pool volume in gallons, or choose rectangle, round or oval and enter the dimensions and average depth.
- Test the current salt level with salt test strips or a digital meter. Use 0 for a newly filled pool.
- Enter the target level from your salt cell's manual. Hayward's AquaRite, for example, lists an ideal level of 3,200 ppm (operating range 2,700–3,400 ppm); many other cells target 3,000–3,500 ppm.
- Choose your bag size. Pool salt is usually sold in 40 lb bags.
The pool salt formula
Salt (lb) = gallons × 8.34 × (target ppm − current ppm) ÷ 1,000,000
One U.S. gallon of water weighs about 8.34 lb (USGS), and ppm means pounds of salt per million pounds of water. So every 1,000 gallons needs about 8.3 lb of salt per 1,000 ppm.
Pool volume formulas
Rectangle: length × width × average depth × 7.48
Round: diameter² × average depth × 5.875
Oval: length × width × average depth × 5.875
There are 7.48 gallons in a cubic foot. Average depth is (shallow end + deep end) ÷ 2. Many pool guides round the round/oval factor to 5.9.
Worked example: new pool
A 10,000 gallon pool filled with fresh water, target 3,200 ppm:
- 10,000 × 8.34 × 3,200 ÷ 1,000,000 = 266.9 lb of salt
- In 40 lb bags: 6.7 → 7 bags
Worked example: topping up
A 32 × 16 ft rectangular pool, 3.5 ft shallow and 6.5 ft deep (average 5 ft), reads 2,000 ppm:
- Volume: 32 × 16 × 5 × 7.48 = 19,150 gallons
- Salt: 19,150 × 8.34 × (3,200 − 2,000) ÷ 1,000,000 = 191.7 lb
- Bags: 5 of 40 lb
Quick reference (0 → 3,200 ppm)
- 5,000 gal: 133 lb (4 bags)
- 10,000 gal: 267 lb (7 bags)
- 15,000 gal: 400 lb (11 bags)
- 20,000 gal: 534 lb (14 bags)
- 30,000 gal: 801 lb (21 bags)
For comparison, seawater is about 35,000 ppm, so a saltwater pool is roughly one-tenth as salty as the ocean.
Signs your salt level is off
If the salt cell shows a low-salt light, chlorine output drops and the water can turn cloudy or green, even though the pump and cell are working. Most cells also shut down or warn at high salt. Test strips can drift, so confirm a surprising reading with a second method before adding a large amount — and remember that a cell's displayed salt level can be off when the cell is scaled with calcium.
How to add salt
- Use pool-grade salt: at least 99% pure sodium chloride, without iodine or anti-caking additives that can stain surfaces.
- Turn the salt cell off while the salt dissolves, run the pump, and pour salt around the shallow end, then brush it toward the main drain.
- Wait about 24 hours with the pump running, then retest before adding more. Adding too much is harder to fix: the only cure is draining and refilling part of the pool.
- Salt does not evaporate. You only lose it through splash-out, backwashing, draining and rain overflow, so routine top-ups are small.
Frequently asked questions
How much salt do I need for a 10,000 gallon pool?
About 267 lb to go from 0 to 3,200 ppm, which is seven 40 lb bags.
How many bags of salt do I need to raise my pool by 500 ppm?
Each 10,000 gallons needs about 42 lb to rise 500 ppm, roughly one 40 lb bag.
What should the salt level be in a saltwater pool?
Most chlorine generators target 3,000–3,500 ppm; 3,200 ppm is a common ideal. Check your cell manual.
How long does pool salt take to dissolve?
Usually about 24 hours with the pump running. Brush undissolved salt and retest the next day.
What happens if I add too much salt to my pool?
Very high salt can trigger cell warnings and taste salty. The only fix is to drain part of the water and refill with fresh water.