Work out the salt to add to hit your saltwater pool's target ppm, and the bags to buy.
Pool and salt levels
Pool volume
Not sure? Run the pool volume calculator first.
Salt now
Enter 0 for a fresh fill.
Target
Your cell's manual has the final word.
Common targets
Estimates only. Not professional advice.
Salt to add
88lb
Pure sodium chloride, dissolved into all 15,000 gal. Nothing is allowed for splash-out, and the figure assumes your reading is right.
Add in stages with the pump running and re-test before the last bag. Overshooting cannot be reversed with a chemical, only with a hose.
Last updated August 11, 2026. Cell windows checked against three manufacturer manuals by our expert review team.
Cell window
A salt cell does not want a number, it wants a band, and the band is narrower than most people expect. Everything below is on one linear ppm scale: the window, your reading, your target, and the width of a single bag of salt.
The window drawn is Hayward's for the AquaRite; Pentair runs higher and Jandy narrower, and all three are compared further down. The bag measure is the part no chart shows: on a small pool it is wider than the window itself, which is how a careful person ends up draining water.
Drain and refill
Salt leaves a pool one way only: with water. Replace a quarter of the water and you keep three quarters of the salt in a pool that is full again, so the reading falls to three quarters of what it was. Every other calculator stops at the dose and leaves this half of the job to a forum thread.
You are under target, so nothing here is a job you have to do. It is the price of an overshoot: one bag too many at 320 ppm would take 9.1% of the water back out to undo.
Assumes the pool is mixed and the fill water carries no salt of its own. Fill water that tests at 200 ppm sets a floor at 200 ppm, so a well-water pool cannot be diluted below whatever the well reads. Waterline drop uses a 5 ft average depth; your own average depth comes off the pool volume calculator.
Dosing practice
The arithmetic is the easy half. These are the seven things that decide whether the number above ends up in the water, in the reading, and in the window.
Aim at the bottom of the window, not the middle. Salt only leaves with water, so a pool that starts at the low edge drifts into the middle on its own as you top up for splash-out. A pool dosed to the top edge has nowhere to go but out through a hose.
Work out what one bag does to your pool before you open two. On the 15,000 gal in the box above, a single 40 lb bag moves the level 320 ppm, and the whole AquaRite window is only 700 ppm wide. On a small above-ground pool one bag can cover the window end to end.
Broadcast over the deep end with the pump running and brush the pile until nothing is left on the floor. Salt sitting on a plaster floor is not in solution, so it is not in the reading, and the cell cannot see it either.
Give it 24 hours before you trust any number. Both manuals ask for a full turnover before the salt reading means anything, and the cell's own sensor is only good to plus or minus 500 ppm even then.
Test at a return, not at the skimmer, and take the sample elbow deep. Surface water near the skimmer is the least mixed water in the pool, which is where a fresh dose is still on its way round.
Buy pool salt, which is 99 percent or better sodium chloride with nothing added. Water softener pellets often carry an anti-caking agent that stains a finish, and rock salt brings insolubles that sink and stay.
Do not know the volume? Get it from the pool volume calculator first. A guess that is 20 percent high puts 20 percent too much salt in the water, and there is no undo.
Bag counts
Two reference tables. The first is the dose from a fresh fill at your own target, which is the figure people come here for. The second is the window three manufacturers actually print, because 3,200 ppm is a Hayward number and not a law.
Your own pool is not starting from zero. 15,000 gal at 2,500 ppm needs 88 lb, or 3 bags, to reach 3,200 ppm.
Rounded up to whole bags, because salt is not sold by the pound. Bag counts move with the bag size in the options panel above.
Hayward AquaRite
2,700–3,400 PPM
IDEAL 3,200
CHECK SALT flashes below 2,700 and the unit is shut down below 2,400
Pentair IntelliChlor
3,000–4,500 PPM
IDEAL 3,400
Low salt below 2,800, no chlorine at all below 2,600
Jandy TruClear
3,000–3,500 PPM
IDEAL 3,000
Warning well below 2,500, corrosion risk above 6,000
Your pool
2,500 PPM NOW
Windows as printed in the AquaRite, IntelliChlor IC15 and TruClear manuals cited below. The dark rule inside each bar is that manual's ideal figure. Jandy's corrosion ceiling of 6,000 ppm sits off the right of this axis.
Test kit
The ones asked with a bag already open, answered against the same formula and the same three manuals the calculator above runs on.
Going from 0 to 3,200 ppm, a 15,000-gallon pool needs about 400 lb of pool salt, or roughly 11 forty-pound bags. If the water already carries salt, you only need the difference, and Jandy's own table agrees: it lists 376 lb to take 15,000 gallons to 3,000 ppm.
It depends on the cell, and the spread is wider than most charts admit. Hayward's AquaRite manual asks for 2,700 to 3,400 ppm with 3,200 optimal, Pentair's IntelliChlor asks for 3,000 to 4,500 with 3,400 ideal, and Jandy's TruClear wants 3,000 to 3,500. Set the target from your own manual rather than from a number you read somewhere.
About 8.3 lb per 1,000 gallons for each 1,000 ppm increase. So a 10,000-gallon pool needs roughly 83 lb to climb 1,000 ppm, and a single 40 lb bag moves that same pool about 480 ppm.
Only by replacing water. There is no chemical that removes salt, so you drain part of the pool and refill with fresh water, which is what Pentair's manual tells IntelliChlor owners to do above 4,500 ppm, 1 ft of depth at a time.
Draining a share of the water removes that same share of the salt, so after refilling, the level falls to the old level times the share you kept. Replace a quarter of the water and 4,000 ppm becomes 3,000. To land on a target exactly, replace 1 minus target over current: going from 4,200 to 3,200 ppm means replacing 23.8 percent of the pool.
Only if the pool overflows. Rain landing in a pool that stays below the coping just raises the level and dilutes nothing you keep, because the salt and the water are both still there. Once water spills over the skimmer or the coping it leaves at full salinity and the rain replaces it at zero, and that is a real dilution you can price like any other drain.
Pool-grade salt that is at least 99.8% pure sodium chloride: evaporated, granulated, non-iodized, with no anti-caking agents, which can stain a finish. Jandy's manual says plainly not to use rock salt, because its insolubles sink and stay on the floor.
You can usually swim right away, but wait until the salt fully dissolves before trusting any number. Run the pump 24 hours and brush any settled salt, then re-test before turning the chlorinator to full output.
Salt itself is pH-neutral, but the chlorine the cell generates is mildly basic, so saltwater pools tend to drift up in pH. Keep testing pH and alkalinity as usual.
Ppm arithmetic
Parts per million is a weight ratio, so both halves of this page come out of one idea: salt divided by water. The dose follows in a line. The dilution takes six.
Ppm is milligrams of salt per kilogram of water, which is the same as pounds per million pounds. So you need the weight of the water, not its volume. A US gallon of water weighs 8.34 lb, and a liter weighs a kilogram, which is why the metric line is shorter.
salt lb = gallons × 8.34 × (target − now) ÷ 1,000,000
salt kg = liters × (target − now) ÷ 1,000,000
Two manufacturers print the same arithmetic as a lookup table, which makes them a free check on this page. Pentair's IC15 guide gives 284.00 lb to take 10,000 gallons from 0 to 3,400 ppm; the line above gives 283.6. Jandy's TruClear manual gives 376 lb to take 15,000 gallons to 3,000 ppm; the line above gives 375.3. Both land inside a quarter of one percent, and the small gap is the water-weight figure each of them rounded differently.
Sodium chloride only. Stabilizer, calcium hardness, total dissolved solids and pH are not modelled, salt is assumed fully dissolved and evenly mixed, and no allowance is made for splash-out during the job.
It trusts your reading. A strip read in shade, a meter that has not been calibrated for sodium chloride, or the cell's own sensor at plus or minus 500 ppm can each put the starting point a whole window out. Two independent tests before a big dose cost nothing next to a drain.
Draining does not remove a fixed amount of salt, it removes a share, because the salt is dissolved in the water that leaves. Write the pool as a volume V holding water at C ppm, drain a fraction f of it, and refill to the line.
The volume cancels, which is the useful part: the answer does not depend on how big the pool is, only on the share of the water you swapped. Replace a quarter and any pool at any level falls to three quarters of that level. The dose that closes what is left then runs on the full V again, because the pool is back up to its line.
Two consequences worth knowing before you rent a pump. The relationship is multiplicative, so halving a reading means replacing half the water and there is no cheaper path made of small steps. And it only reaches zero if the fill water is zero: fill water carrying S ppm gives C × (1 − f) + S × f, so your hose sets the floor.
Four pools
Every figure below comes out of the calculator on this page, from the volume and the two readings printed beside it. The last one is the case with no dose at all.
15,000 gal · 0 TO 3,200 PPM
400lb
11 BAGS · +3,200 PPM
A fresh conversion needs a full salt charge. Add salt with the pump running and brush to dissolve.
20,000 gal · 2,600 TO 3,200 PPM
100lb
3 BAGS · +600 PPM
After rain or splash-out, levels drift down. Top up in small doses and re-test before adding more.
5,000 gal · 1,000 TO 3,000 PPM
83lb
3 BAGS · +2,000 PPM
Smaller pools reach target with far less salt, so add half, circulate, then re-test.
15,000 gal · 4,200 TO 3,200 PPM
0lb
1,000 PPM OVER · DRAIN 23.8%
Nothing to add. The only route back is replacing water, and 4,200 down to 3,200 is 23.8 percent of the pool.
Overshoot
This is the one page section worth reading before you buy rather than after. Salt is the only pool chemical with no reverse gear, so every mistake below is paid for with a pump, a hose and a water bill instead of another trip to the store.
The full target dosed as though the pool were fresh
Water already carrying 2,500 ppm needs the gap, not the target. Dosing 3,200 into a pool at 2,500 lands you near 5,700, which is past every shutdown threshold on this page.
Bags emptied into the skimmer
Undissolved salt goes through the pump and the cell as a slug of brine. Broadcast it over the deep end with the pump running and brush the pile until it is gone.
A whole bag added to a small pool
One bag is a fixed weight and a small pool is a small denominator, so the step gets bigger as the pool gets smaller. Check the bag measure on the drawing above before you open the second one.
The cell's own salt readout treated as a test
The IntelliChlor manual puts its salt sensor at plus or minus 500 ppm, which is most of the width of a working window. Test with strips or a meter and use the readout as a sanity check.
A printed dose chart read instead of the arithmetic
Charts are lookups and lookups carry typos. The IC15 guide's own table repeats the 20,000 gallon figures on its 22,000 gallon row, so 22,000 gallons reads 568 lb when the arithmetic gives 625.
Water softener salt or rock salt used
Anti-caking agents stain a finish and the insolubles in rock salt sink and stay. Jandy's manual says plainly not to use rock salt. Buy 99 percent or better sodium chloride sold for pools.
Salt topped up after heavy rain without a test
Rain does not dilute a pool. Rain that pushes water out over the skimmer does, because that water leaves at full salinity and rain replaces it at zero. Test first, then dose the gap.
A product bought to lower the salt level
There is no such product. Salt leaves with water and by no other route, which is what the drain and refill table on this page prices.
Season drift
Salt does not evaporate, break down or get used up making chlorine: the cell splits it and the pool puts it back together. So a reading that has moved means water has moved, and knowing which kind tells you whether to dose or to wait.
Water leaves, salt stays, so the reading climbs. Topping the level back up with a hose puts the reading back where it was. Over a season the pair roughly cancel, which is why Hayward's manual says salt is not lost to evaporation.
Water leaves at full salinity and the hose replaces it at nearly zero, so this is the everyday loss. A busy pool drifts down a few hundred ppm across a summer.
A backwash cycle can send several hundred gallons to waste at full salinity. Two or three backwashes is a measurable dilution, and it is the one loss you schedule yourself.
The overflow is pool water and the replacement is rain. A pool that spills an inch of its depth over the coping has replaced that share of its water, exactly as if you had drained it.
Dropping the level below the skimmer for winter and refilling in spring is a partial drain and refill, so it is a dilution event with a known fraction. Price it on the table above before you buy bags in April.
Both Pentair and Jandy want the surface cured before the cell runs, about a month for plaster. Salt can go in and be dissolved, but chlorinate by hand until the wait is up.
Test monthly through the season and again after anything that moved a lot of water. If the reading has dropped, the dose is at the top of this page. If it has climbed past the window, the fix is the drain and refill table, and the volume it needs comes from the pool volume calculator.
Disclaimer
These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.
Sources