How much salt do I need for my pool?

Pounds of salt = gallons × 8.34 × (target ppm − current ppm) ÷ 1,000,000. For a 20,000 gallon pool going from 0 to 3,200 ppm: 20,000 × 8.34 × 3,200 ÷ 1,000,000 = 533.8 lb, which is 534 lb of salt (14 bags of 40 lb). From 2,500 ppm the same pool needs only 117 lb of salt (3 bags of 40 lb).

Where does the 8.34 come from?

A US gallon of water weighs about 8.34 lb. A salt level in ppm is pounds of salt per million pounds of water, so a gallon of water at 1 ppm holds 8.34 ÷ 1,000,000 lb of salt, and the pool holds that times its gallons. Multiply by the number of ppm to add and you have the formula. Some guides write 8.35 or 8.3, which changes the answer by well under 1%.

Does this match the salt chart from the chlorinator maker?

It matches the one chart checked. Hayward’s AquaRite chart lists 533 lb for a 20,000 gallon pool at 3,200 ppm and this calculator gives 534 lb: the same within a pound. Morton’s 40 lb bag label says 480 ppm per bag in 10,000 gallons, and the formula gives 480 ppm. Makers’ charts are for their own cell and target, so follow the chart in your manual if it differs from this page.

What should my target salt level be?

Use the level in your chlorinator’s manual or on its cell. Hayward gives 2,700 to 3,400 ppm for AquaRite with 3,200 ppm ideal, which is the default here. Pentair’s IntelliChlor salt table is worked to 3,400 ppm. Other makers and other models of the same maker differ, and some sources quote different windows for the same product, so check yours. A level too low makes the cell produce less chlorine or shut down; too high can shut the unit down and give the water a salty taste.

My salt is too high. What do I do?

Salt does not leave the pool on its own, so you dilute it: drain part of the water and refill with fresh water. The share to replace is 1 − target ÷ current. A 20,000 gallon pool at 4,000 ppm with a 3,200 ppm target needs 20% of the water replaced, about 4,000 gallons. Drain a bit less than the figure, refill, run the pump, retest and repeat if needed, because it is easier to add salt than to remove it. Check local rules before draining a pool.

How many bags of pool salt is that?

The pounds divided by the bag size, rounded up. A 40 lb bag raises a 20,000 gallon pool by about 240 ppm, so 534 lb of salt (14 bags of 40 lb). With 50 lb bags the same job is 534 lb of salt (11 bags of 50 lb). In a 10,000 gallon pool one 40 lb bag raises the level about 480 ppm. Rounding up means you end up slightly over; for the last bag you can pour in part of it and retest.

What if my pool volume is in litres?

Pick litres in the volume unit and the calculator converts to US gallons (1 US gallon is 3.785411784 L). A rule of thumb in metric: each 1,000 ppm is about 1 kg of salt per 1,000 litres, so 3,200 ppm is about 3.2 kg per 1,000 litres. A 75,000 L pool from 500 to 3,200 ppm needs 446 lb of salt (12 bags of 40 lb), or 202 kg.

How do I add the salt, and when do I retest?

Sodium chloride that is more than 99% pure, without anti-caking additives or iodine, is what Hayward asks for. Add it with the pump running and brush it around so it dissolves rather than sitting in a pile on the floor, then give it time to circulate (about a day is commonly advised) before you test. Add in two stages if you are unsure of the volume or the starting level, and retest with a salt meter or strip. Follow your chlorinator’s manual for where to pour it with the cell on or off.

Why does the level drop over the season?

Salt leaves with the water, not with the chlorine it makes: splash-out, backwashing, draining and overflow from rain all take some. A top-up after heavy rain or a partial drain is normal. Retest a few times a season rather than adding salt by the calendar.

Does this cover chlorine and other chemicals?

No. It only works out the salt. Chlorine output, stabiliser and pH depend on your chlorinator and the pool, so follow its manual and the directions on the products you use.

Pool Salt Calculator: How Many Pounds and Bags of Salt?

A 20,000 gallon saltwater pool at 0 ppm needs 534 lb of salt (14 bags of 40 lb) to reach 3,200 ppm, the level Hayward gives as ideal for its AquaRite chlorinator. That is 20,000 gal × 8.34 lb of water per gallon × 3,200 ppm ÷ 1,000,000 = 533.8 lb, and the bag count is rounded up. Enter your pool volume, the salt level you tested and the level your chlorinator wants. If the pool is already above the target, salt cannot be taken out, so the calculator shows how much water to replace instead. Don’t know your volume? Work it out with the pool volume calculator.

Figures based on the sources listed belowUpdated 2026-10-13How we calculate

Pool volume

The gallons (or litres) of water in the pool, in the unit picked below. Not sure? The pool volume calculator works it out from the size and depth of the water.

Volume unitThe pounds are worked from US gallons (8.34 lb of water each); litres and imperial gallons are converted first.

Current salt level (ppm)

From a salt test strip, a digital salt meter or your chlorinator’s display. Enter 0 for a new pool filled with fresh water (fill water is not truly 0 ppm, so retest before you add the last bag). A chlorinator’s display can be off, so confirm it with a test.

Target salt level (ppm)

Use the level your chlorinator’s manual or cell label gives. Hayward lists 2,700 to 3,400 ppm for AquaRite with 3,200 ppm ideal; Pentair’s IntelliChlor salt table is worked to 3,400 ppm. Other makers differ, so check yours.

Bag size (lb)

Pool salt is commonly sold in 40 lb bags. Read the weight on the bag if yours is different.

534 lb of salt (14 bags of 40 lb)

Bags: 14 bags of 40 lb (560 lb, 26.2 lb more than needed)
Salt in kilograms: 242.1 kg (533.8 lb × 0.45359)
Salt level: 0 ppm now, 3,200 ppm once the salt has dissolved and mixed
One bag raises the level by: about 240 ppm in 20,000 US gal
Target check: 3,200 ppm is inside the 2,700 to 3,400 ppm window Hayward gives for AquaRite

Shopping list

Pool salt, 40 lb bag
Salt test strips for pools
Digital salinity meter
Pool brush (to spread salt)
Submersible pump (to lower the level)

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Pounds of salt by pool size

To 3,200 ppm with 40 lb bags, worked by this calculator and rounded to the nearest pound. The last column is how much one 40 lb bag raises the level in that pool. The 20,000 gallon row agrees with the 533 lb in Hayward’s chart.
Pool volume	From 0 ppm	From 2,500 ppm	ppm per bag
10,000 gal	267 lb (7 bags)	58 lb (2 bags)	480
15,000 gal	400 lb (11 bags)	88 lb (3 bags)	320
20,000 gal	534 lb (14 bags)	117 lb (3 bags)	240
25,000 gal	667 lb (17 bags)	146 lb (4 bags)	192
30,000 gal	801 lb (21 bags)	175 lb (5 bags)	160

Salt for a 20,000 gallon pool by ppm to add

The salt scales in a straight line with the rise in ppm. US gallons, 40 lb bags, rounded to the nearest pound or kilogram.
Rise in level	Salt	In kilograms	Bags
100 ppm	17 lb	8 kg	1 bags
200 ppm	33 lb	15 kg	1 bags
500 ppm	83 lb	38 kg	3 bags
1,000 ppm	167 lb	76 kg	5 bags
2,000 ppm	334 lb	151 kg	9 bags
3,200 ppm	534 lb	242 kg	14 bags

Water to replace when the level is too high

Target 3,200 ppm in a 20,000 gallon pool. The share of water to drain and refill with fresh water is 1 − 3,200 ÷ current level. This assumes fresh water with no salt in it and thorough mixing: retest afterwards.
Current level	Water to replace	In a 20,000 gal pool
3,400 ppm	5.9%	1,176 gal
3,600 ppm	11.1%	2,222 gal
4,000 ppm	20%	4,000 gal
4,500 ppm	28.9%	5,778 gal
5,000 ppm	36%	7,200 gal
6,000 ppm	46.7%	9,333 gal

Methodology & assumptions

Salt level is measured in parts per million (ppm) by weight: pounds of salt per million pounds of water. A US gallon of water weighs 8.34 lb, so a pool of V gallons holds V × 8.34 lb of water, and raising the level by a number of ppm takes: pounds of salt = V × 8.34 × (target ppm − current ppm) ÷ 1,000,000. For 20,000 gallons from 0 to 3,200 ppm that is 20,000 × 8.34 × 3,200 ÷ 1,000,000 = 533.76 lb. Hayward’s published AquaRite salt chart lists 533 lb for a 20,000 gallon pool at 3,200 ppm (the chart’s figure as read from a dealer-hosted Hayward presentation; check the chart in your manual), within a pound of this result. Morton’s 40 lb bag label states that a bag raises the level by 480 ppm in 10,000 gallons, and the formula gives 480 ppm. The weight of the salt itself is ignored, as the makers’ charts do: strictly ppm = salt ÷ (water + salt), which would add about 0.3% at 3,200 ppm. The weight of a gallon changes a little with temperature (about 8.3 lb for warm pool water), which is well inside the accuracy of a salt test. Bags: the pounds divided by the bag size, rounded up to whole bags. The pounds shown are rounded to the nearest pound. Litres and imperial gallons are converted to US gallons first (1 US gal = 3.785411784 L, 1 imperial gal = 4.54609 L). Too high: salt does not evaporate or filter out, so the only way down is to replace some of the water with fresh water. If a fraction f of the water is drained and refilled with salt-free water, the level becomes current × (1 − f), so f = 1 − target ÷ current. Fresh fill water is not truly salt-free, and a pool is never mixed instantly, so retest after refilling. Retest after adding salt too: test strips and chlorinator displays are only accurate to a few hundred ppm, and salt is lost with splash-out, backwashing and draining, which is why the level falls over a season. Target levels: Hayward gives 2,700 to 3,400 ppm for AquaRite with 3,200 ppm ideal. Pentair’s IntelliChlor manual builds its salt table to 3,400 ppm, and secondary sources give other windows for Pentair, so the 3,200 ppm default is Hayward’s figure, not a universal one: use the number in your chlorinator’s manual or on its cell. This calculator covers the salt only, not the rest of the water chemistry.

Hayward, AquaRite salt chlorination system owner’s manual (document 092538): the ideal salt level is 2,700 to 3,400 ppm with 3,200 ppm optimum, a chart of the salt to add by pool size, and the advice to use sodium chloride that is more than 99% pure without anti-caking additives or iodine
Hayward, 206 Salt Chlorination training presentation (document CHLOR206d, hosted by Royal Swimming Pools): the chart row for 20,000 gallons begins 533, 500, 466 pounds. Read from a search result, not from the full document, so check the chart in your own manual
Pentair, IntelliChlor Salt Chlorine Generator Model IC15 Installation and User’s Guide, Table 1: approximate pounds of salt needed to reach 3,400 ppm. The recommended window was not confirmed from the manual itself, so use the one on your cell
Morton Salt, Professional’s Choice Pool Salt 40 lb bag, retailer listing (ShopRite): one bag raises the salt level by 480 ppm in 10,000 gallons, which the formula reproduces within 0.1%
Weight of water: 8.34 lb per US gallon (a US gallon is 231 cubic inches, about 3.785 L, and water at room temperature weighs about 1 kg per litre). A standard figure used in pool and water treatment calculations; it is about 0.5% lower for warm water
Dilution: replacing a fraction of the water with salt-free water scales the level by (1 − fraction). The calculator’s own derivation from that mass balance, not a maker’s figure

How to work out how much salt to add to a pool

Find the pool volume. Use the volume from your pool’s papers, or work it out from the size and depth of the water with the pool volume calculator.
Test the current salt level. Use a salt test strip or digital meter. Do not rely only on the chlorinator’s display.
Choose the target. Use the ppm in your chlorinator’s manual or on its cell. Hayward gives 3,200 ppm as ideal for AquaRite.
Work out the pounds. Gallons × 8.34 × (target − current) ÷ 1,000,000 gives pounds of salt. Divide by the bag size and round up for the bags.
Add, circulate and retest. Pour the salt in with the pump running, brush it around, wait for it to dissolve and mix, then test again. If the level is above target, replace 1 − target ÷ current of the water instead.

Worked examples

Project	Result
New 20,000 gallon pool, 0 to 3,200 ppm, 40 lb bags	534 lb of salt (14 bags of 40 lb), 533.8 lb before rounding
10,000 gallon pool, 0 to 3,200 ppm, 40 lb bags	267 lb of salt (7 bags of 40 lb), about 480 ppm per bag
15,000 gallon pool topping up from 2,500 to 3,200 ppm	88 lb of salt (3 bags of 40 lb)
20,000 gallon pool topping up from 2,500 to 3,200 ppm	117 lb of salt (3 bags of 40 lb), 116.8 lb before rounding
25,000 gallon pool from 1,000 to 3,400 ppm	500 lb of salt (13 bags of 40 lb)
20,000 gallon pool, 0 to 3,200 ppm, 50 lb bags	534 lb of salt (11 bags of 50 lb)
75,000 litre pool from 500 to 3,200 ppm	446 lb of salt (12 bags of 40 lb), 202 kg
10,000 imperial (UK) gallon pool from 500 to 3,200 ppm	270 lb of salt (7 bags of 40 lb)
20,000 gallon pool at 4,000 ppm with a 3,200 ppm target	Too high: dilute with fresh water: replace 20% of the water, about 4,000 gallons

Frequently asked questions

How much salt do I need for my pool?: Pounds of salt = gallons × 8.34 × (target ppm − current ppm) ÷ 1,000,000. For a 20,000 gallon pool going from 0 to 3,200 ppm: 20,000 × 8.34 × 3,200 ÷ 1,000,000 = 533.8 lb, which is 534 lb of salt (14 bags of 40 lb). From 2,500 ppm the same pool needs only 117 lb of salt (3 bags of 40 lb).
Where does the 8.34 come from?: A US gallon of water weighs about 8.34 lb. A salt level in ppm is pounds of salt per million pounds of water, so a gallon of water at 1 ppm holds 8.34 ÷ 1,000,000 lb of salt, and the pool holds that times its gallons. Multiply by the number of ppm to add and you have the formula. Some guides write 8.35 or 8.3, which changes the answer by well under 1%.
Does this match the salt chart from the chlorinator maker?: It matches the one chart checked. Hayward’s AquaRite chart lists 533 lb for a 20,000 gallon pool at 3,200 ppm and this calculator gives 534 lb: the same within a pound. Morton’s 40 lb bag label says 480 ppm per bag in 10,000 gallons, and the formula gives 480 ppm. Makers’ charts are for their own cell and target, so follow the chart in your manual if it differs from this page.
What should my target salt level be?: Use the level in your chlorinator’s manual or on its cell. Hayward gives 2,700 to 3,400 ppm for AquaRite with 3,200 ppm ideal, which is the default here. Pentair’s IntelliChlor salt table is worked to 3,400 ppm. Other makers and other models of the same maker differ, and some sources quote different windows for the same product, so check yours. A level too low makes the cell produce less chlorine or shut down; too high can shut the unit down and give the water a salty taste.
My salt is too high. What do I do?: Salt does not leave the pool on its own, so you dilute it: drain part of the water and refill with fresh water. The share to replace is 1 − target ÷ current. A 20,000 gallon pool at 4,000 ppm with a 3,200 ppm target needs 20% of the water replaced, about 4,000 gallons. Drain a bit less than the figure, refill, run the pump, retest and repeat if needed, because it is easier to add salt than to remove it. Check local rules before draining a pool.
How many bags of pool salt is that?: The pounds divided by the bag size, rounded up. A 40 lb bag raises a 20,000 gallon pool by about 240 ppm, so 534 lb of salt (14 bags of 40 lb). With 50 lb bags the same job is 534 lb of salt (11 bags of 50 lb). In a 10,000 gallon pool one 40 lb bag raises the level about 480 ppm. Rounding up means you end up slightly over; for the last bag you can pour in part of it and retest.
What if my pool volume is in litres?: Pick litres in the volume unit and the calculator converts to US gallons (1 US gallon is 3.785411784 L). A rule of thumb in metric: each 1,000 ppm is about 1 kg of salt per 1,000 litres, so 3,200 ppm is about 3.2 kg per 1,000 litres. A 75,000 L pool from 500 to 3,200 ppm needs 446 lb of salt (12 bags of 40 lb), or 202 kg.
How do I add the salt, and when do I retest?: Sodium chloride that is more than 99% pure, without anti-caking additives or iodine, is what Hayward asks for. Add it with the pump running and brush it around so it dissolves rather than sitting in a pile on the floor, then give it time to circulate (about a day is commonly advised) before you test. Add in two stages if you are unsure of the volume or the starting level, and retest with a salt meter or strip. Follow your chlorinator’s manual for where to pour it with the cell on or off.
Why does the level drop over the season?: Salt leaves with the water, not with the chlorine it makes: splash-out, backwashing, draining and overflow from rain all take some. A top-up after heavy rain or a partial drain is normal. Retest a few times a season rather than adding salt by the calendar.
Does this cover chlorine and other chemicals?: No. It only works out the salt. Chlorine output, stabiliser and pH depend on your chlorinator and the pool, so follow its manual and the directions on the products you use.