Pool Salt Calculator
How many bags of salt to reach your chlorinator's target ppm from the level you tested, with Hayward and Pentair targets, pool volume by shape and a shock dose.
Pool Salt Calculator: with the default inputs, bags of salt to add is 4.
Gallons mode only. If you don't know it, pick a shape above instead.
Round pools only.
Halfway between the shallow and deep ends for a pool with one continuous slope. A pool with a flat deep end holds more than that, so weight the average by area.
From a test strip, a drop kit or a lab. Don't use the chlorinator's own display to dose from — Pentair's own manual puts its sensor at ±500 ppm.
The brands genuinely disagree, so this sets the target. Your own manual wins over anything here.
Used only when the chlorinator is set to “Something else”.
Hayward's manual says pool salt comes in 40–80 lb bags; every US pool-salt product we could check is 40 lb. Use only sodium chloride over 99.0% pure.
Rounded up — you cannot buy part of a bag.
- Salt needed
- 133.5 lbThe exact amount before rounding to whole bags.
- Pool volume
- 20,000 gal
- Salt to make up (ppm)
- 800Target minus what you tested.
- Level after those whole bags (ppm)
- 3,359Whole bags rarely land exactly on the target.
- One bag raises this pool by (ppm)
- 240
- Water to replace if the salt is too high
- 0 galDraining and refilling is the only way down — nothing removes salt from water.
- Free chlorine to add for breakpoint (ppm)
- 5About 10 × the combined chlorine (CDC Model Aquatic Health Code).
- Shock product for that
- 0.83 lb
Assumptions
- ppm means mg/L, so the dose is a unit conversion — gallons × ppm × 8.345404 ÷ 1,000,000 — with no water-density or temperature term.
- Salt targets are as printed in the Hayward and Pentair manuals listed under Sources. Your own manual overrides them.
- Volumes use the geometric factors: 7.48052 gallons per cubic foot, and π/4 of that for a round or a true elliptical pool. Hayward's own chart rounds these to 7.5 and 5.9 and uses 6.7 for an oval, which runs about 14% above a true ellipse — if you are matching their chart, expect that difference.
- Average depth means the volume-weighted average. Halfway between the ends is right for one continuous slope and low for a pool with a flat deep end.
- Fill water is assumed to contain no salt of its own; well water and softened water sometimes do.
- Bags round up. Salt is cheap, but overshooting can only be fixed by draining, so add one bag short of the count and finish by test.
- This is arithmetic on the numbers you typed. It does not replace a test kit, and it is not a substitute for your equipment manuals or a pool professional.
| Raise by | Pounds | 40-lb bags |
|---|---|---|
| 100 ppm | 8.3 | 0.21 |
| 200 ppm | 16.7 | 0.42 |
| 400 ppm | 33.4 | 0.83 |
| 600 ppm | 50.1 | 1.25 |
| 800 ppm | 66.8 | 1.67 |
| 1,000 ppm | 83.5 | 2.09 |
| 1,500 ppm | 125.2 | 3.13 |
| 2,000 ppm | 166.9 | 4.17 |
| 2,500 ppm | 208.6 | 5.22 |
| 3,000 ppm | 250.4 | 6.26 |
| 3,200 ppm | 267.1 | 6.68 |
Scale it: a 20,000 gallon pool needs twice these, a 15,000 gallon pool one and a half times. 83.45 lb per 10,000 gallons raises salt by 1,000 ppm.
| Cell | Ideal | Range |
|---|---|---|
| Hayward AquaRite | 3,200 ppm | 2,700–3,400 ppm |
| Hayward AquaRite 100 | 3,200 ppm | 1,500–4,500 ppm |
| Hayward AquaRite S3 | 3,200 ppm | 2,700–3,400 ppm |
| Pentair IntelliChlor | 3,600 ppm | 3,600–4,500 ppm |
Hayward's AquaRite manual: “The ideal salt level is between 2700-3400 ppm … with 3200 ppm being optimal.” Salt starts to taste salty around 3,500–4,000 ppm.
How this is worked out
The formula
Pounds of salt = gallons × (target ppm − current ppm) × 8.345404 ÷ 1,000,000 where 8.345404 = 3.785411784 L per gallon ÷ 453,592.37 mg per pound, and ppm means mg/L Bags = pounds ÷ bag weight, rounded up Pool volume (gallons) rectangular = length × width × average depth × 7.48052 round or oval = π ÷ 4 × length × width × average depth × 7.48052 To come down: replace gallons × (current − target) ÷ current with fresh water Breakpoint shock = 10 × combined chlorine, in ppm of free chlorine
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Pool volume
- Choose one of 4 options.I know the gallons · Rectangular — length × width × average depth · Round — diameter × average depth · Oval — length × width × average depth
- Pool volume
- Gallons mode only. If you don't know it, pick a shape above instead.in gal, L, m³ · 0 or more · defaults to 20000
- Length
- A number.in ft, m, in, cm · 0 or more · defaults to 32
- Width
- A number.in ft, m, in, cm · 0 or more · defaults to 16
- Diameter
- Round pools only.in ft, m, in, cm · 0 or more · defaults to 24
- Average depth
- Halfway between the shallow and deep ends for a pool with one continuous slope. A pool with a flat deep end holds more than that, so weight the average by area.in ft, m, in, cm · 0 or more · defaults to 5
- Salt level you tested
- From a test strip, a drop kit or a lab. Don't use the chlorinator's own display to dose from — Pentair's own manual puts its sensor at ±500 ppm.from 0 to 20000 · defaults to 2400
- Your chlorinator
- The brands genuinely disagree, so this sets the target. Your own manual wins over anything here.Hayward AquaRite — 2,700–3,400 ppm, 3,200 optimal · Hayward AquaRite 100 — 1,500–4,500 ppm, 3,200 ideal · Hayward AquaRite S3 — alarms at 2,700 and 3,400, 3,200 optimal · Pentair IntelliChlor — 3,600–4,500 ppm, 3,600 ideal · Something else — enter the target yourself
- Target salt level
- Used only when the chlorinator is set to “Something else”.from 100 to 10000 · defaults to 3200
- Bag size
- Hayward's manual says pool salt comes in 40–80 lb bags; every US pool-salt product we could check is 40 lb. Use only sodium chloride over 99.0% pure.40 lb (the standard US pool-salt bag) · 50 lb (water-softener salt) · 80 lb
- Combined chlorine (chloramines)(under More options)
- Total chlorine minus free chlorine. The MAHC says to act above 0.4 ppm. Enter 0 to skip the shock dose.from 0 to 20 · defaults to 0.5
- Available chlorine on the label(under More options)
- Every shock product prints this percentage on the bag. Leave it at 100 and you get pounds of pure available chlorine instead.a percentage · from 1 to 100 · defaults to 100
What you get back
- Bags of salt to addmain answer
- Rounded up — you cannot buy part of a bag.
- Salt needed
- The exact amount before rounding to whole bags.
- Pool volume
- Salt to make up (ppm)
- Target minus what you tested.
- Level after those whole bags (ppm)
- Whole bags rarely land exactly on the target.
- One bag raises this pool by (ppm)
- Water to replace if the salt is too high
- Draining and refilling is the only way down — nothing removes salt from water.
- Free chlorine to add for breakpoint (ppm)
- About 10 × the combined chlorine (CDC Model Aquatic Health Code).
- Shock product for that
What this assumes
- ppm means mg/L, so the dose is a unit conversion — gallons × ppm × 8.345404 ÷ 1,000,000 — with no water-density or temperature term.
- Salt targets are as printed in the Hayward and Pentair manuals listed under Sources. Your own manual overrides them.
- Volumes use the geometric factors: 7.48052 gallons per cubic foot, and π/4 of that for a round or a true elliptical pool. Hayward's own chart rounds these to 7.5 and 5.9 and uses 6.7 for an oval, which runs about 14% above a true ellipse — if you are matching their chart, expect that difference.
- Average depth means the volume-weighted average. Halfway between the ends is right for one continuous slope and low for a pool with a flat deep end.
- Fill water is assumed to contain no salt of its own; well water and softened water sometimes do.
- Bags round up. Salt is cheap, but overshooting can only be fixed by draining, so add one bag short of the count and finish by test.
- This is arithmetic on the numbers you typed. It does not replace a test kit, and it is not a substitute for your equipment manuals or a pool professional.
About this calculator
Salt in a pool is a concentration, so the dose depends on two numbers and nothing else: how many gallons you have, and how far below the target you tested. One pound of salt in a million pounds of water is 1 ppm — and because a US gallon is 3.785 litres and a pound is 453,592 mg, that works out to 83.45 lb per 10,000 gallons for every 1,000 ppm. Everything on this page is that one line of arithmetic.
The target is your chlorinator's, not ours
The brands genuinely disagree, and it matters. Hayward's AquaRite manual says 2,700–3,400 ppm with 3,200 optimal. The newer AquaRite 100 widens that to 1,500–4,500. Pentair's IntelliChlor asks for 3,600 ppm and warns about corrosion above 4,500. Dosing a Pentair cell to Hayward's 3,200 leaves it running a low-salt light. Pick your cell above, or read the sticker on the unit — that number beats any general advice.
Add it in the deep end, with the pump running
Brush the salt around the deep end rather than dumping it in one spot, leave the pump running, and give it a day to dissolve and circulate before you test again. If the whole-bag count would overshoot the top of the range, add one bag fewer, wait, test, and finish with part of the last one. Overshooting is the expensive mistake.
There is no way to take salt back out
Hayward's manual puts it plainly: the only way to lower the salt concentration is to partially drain the pool and refill with fresh water. No chemical removes it. Salt is also not consumed by making chlorine — the cell splits it and it recombines — so you only lose it to splash-out, backwashing, draining and rain overflow, never to evaporation. That is why a salt pool needs topping up once or twice a season, not weekly.
The shock box
Under More options there is a breakpoint dose. Combined chlorine (chloramines) is the total chlorine minus the free chlorine, and it is what makes a pool smell like a pool. The CDC's Model Aquatic Health Code defines breakpoint as adding roughly ten times the combined chlorine as free chlorine. Enter the percentage of available chlorine printed on your shock bag and you get pounds of product; leave it at 100% and you get pounds of pure available chlorine.
This is arithmetic, not a water test
It cannot see your pool. It assumes the reading you typed is right, that your fill water has no salt of its own, and that nothing else is off. Test the water, dose from the test, and retest after a day — and keep an eye on stabiliser too, since cyanuric acid and salt tend to drift down together.
Frequently asked questions
▸How much salt does a 20,000 gallon pool need?
83.45 lb raises 10,000 gallons by 1,000 ppm, so 20,000 gallons needs about 167 lb per 1,000 ppm. Going from 2,400 to 3,200 ppm — an 800 ppm lift — is about 133 lb, or four 40-lb bags.
▸What salt level should a saltwater pool be?
Whatever your chlorinator's manual says, because they differ. Hayward's AquaRite wants 2,700–3,400 ppm with 3,200 optimal; Pentair's IntelliChlor wants 3,600–4,500 with 3,600 ideal. Too low and the cell stops making chlorine; too high and you risk corrosion and a salty taste.
▸How do I lower the salt level in my pool?
Drain part of the pool and refill with fresh water. Hayward's manual says that is the only way, and it is — nothing takes salt back out of water. Replacing a fraction (current − target) ÷ current of the volume gets you there, and the calculator works out the gallons.
▸Do I have to keep adding salt?
Very little. Making chlorine does not consume the salt — the cell splits it and it recombines — and none of it evaporates. You only lose salt with water you lose: splash-out, backwashing, draining after heavy rain. Most pools need a top-up once or twice a season.
▸What kind of salt, and what size bag?
Sodium chloride at 99.0% purity or better, sold as pool salt or as clean water-softener salt. Hayward's manual says 40–80 lb bags; the standard US pool-salt bag is 40 lb. Avoid salt with anti-caking agents or iodine.
▸How much shock is a breakpoint dose?
The CDC's Model Aquatic Health Code defines breakpoint as free chlorine of roughly ten times the combined chlorine. At 0.5 ppm of chloramines that is 5 ppm of free chlorine, which in a 20,000 gallon pool is about 0.83 lb of pure available chlorine — divide by your product's label percentage for pounds of product.
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