Pool & spa
Pool Chemical Cost Calculator
What a season of chemicals costs, starting from the pool volume, which you can enter directly or have worked out from the shape.
Result
Volume is the input everything else scales from, which is why getting it from the shape is offered rather than asking for a number most owners do not know. Average depth is the mean of the two ends, correct for a constant slope and approximate for a pool with a distinct deep end shelf. Chemical demand is not purely a function of volume though: sunlight, bather load, rainfall, temperature and how well the water is balanced all change consumption substantially, and a stabiliser level that is too low will burn chlorine far faster than the volume suggests. Treat the dose rate as your own observed figure rather than a specification.
Get a Free Business AuditHow the calculation works
Volume comes first, from the shape or entered directly, since every chemical quantity scales from it. Sanitiser cost is then volume in ten-thousand-gallon units times the weekly dose rate times the price times the weeks in the season, adjusted by sanitiser type because a salt cell, tablets, granular and liquid deliver very different amounts per unit purchased. Balancers, shock and algaecide are added as monthly figures scaled to the season length.
What moves the number
- Sanitiser type, since a salt system buys far less sanitiser than a liquid chlorine pool.
- Volume, which scales every quantity.
- Season length, which varies enormously by climate.
- Stabiliser level, because a poorly stabilised pool consumes chlorine far faster.
Where this one goes wrong
Chemical consumption is not purely a function of volume. Sunlight, bather load, rainfall, temperature and how well the water is balanced all change it substantially, and cyanuric acid level in particular can double or halve chlorine demand on the same pool. A dose rate observed on your own pool across a season is worth far more than a typical figure. Balancers are the line owners underestimate, because no single purchase is large while the season total is a meaningful share of the chemistry bill.
Before you quote
- Use your own observed weekly dose rather than a generic rate.
- Check stabiliser level, which strongly affects chlorine consumption.
- Count balancers, which accumulate quietly across a season.
Where the rules come from
Questions
About this calculator
How many gallons is my pool?
For a rectangular pool it is length times width times average depth times 7.48, since a cubic foot holds about 7.48 gallons. For a round pool use pi times the radius squared instead of length times width. Average depth is the mean of the shallow and deep ends for a pool with a constant slope.
Why does my chlorine use vary so much week to week?
Sunlight and bather load are the main causes, and stabiliser level is the one people miss. Chlorine breaks down rapidly in ultraviolet light, and without enough cyanuric acid to protect it the same dose disappears far faster. A hot week with a full pool and heavy rain behaves nothing like a quiet cool one.
Is a salt system cheaper?
Salt reduces recurring sanitiser purchases because the cell generates chlorine from the salt already in the water, but the cell is a consumable that needs periodic replacement and the system has an up front cost. Compare the recurring saving against the cell replacement cost over its expected life rather than on the weekly figure alone.
Do balancers really cost that much?
They are easy to underestimate because no single purchase is large. Acid or soda ash, alkalinity increaser, calcium and stabiliser across a full season add up to a meaningful share of the total, and a pool that is chronically out of balance consumes more of everything, including sanitiser.
The formula
gallons = length x width x average depth x 7.48 (round: pi x radius squared x average depth); sanitiser = gallons / 10,000 x units per week x price x weeks
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How to use this calculator
- Pool volume. Enter your own figure; the page starts at Work it out from a rectangular pool.
- Length (ft). Enter your own figure; the page starts at 32.
- Width (ft). Enter your own figure; the page starts at 16.
- Shallow end depth (ft). Enter your own figure; the page starts at 3.5.
- Deep end depth (ft). Enter your own figure; the page starts at 7.
- Sanitiser. Enter your own figure; the page starts at Liquid chlorine.
The result updates as you type, so you can try a figure, see what it does to chemical cost for the season, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Pool volume | Work it out from a rectangular pool |
| Length (ft) | 32 |
| Width (ft) | 16 |
| Shallow end depth (ft) | 3.5 |
| Deep end depth (ft) | 7 |
| Sanitiser | Liquid chlorine |
| Sanitiser price per unit | $5.5 |
| Sanitiser units per week per 10,000 gallons | 2.5 |
| Balancers per month | $35 |
| Shock and algaecide per month | $28 |
| Weeks in the season | 26 |
What comes out
| Result | Value |
|---|---|
| Chemical cost for the season main result | $1,096 |
| Pool volume (gallons) | 20,108 |
| Sanitiser for the season | $718.85 |
| Balancers, shock and algaecide | $376.99 |
| Cost per week | $42.15 |
| Season cost per 10,000 gallons | $544.98 |
A 20,108 gallon pool costs about $1,096 in chemicals for a 26 week season: $718.85 of sanitiser and $376.99 of balancers, shock and algaecide. That is $42.15 a week.
How sensitive the answer is
Holding everything else steady and changing only sanitiser price per unit, this is what happens to chemical cost for the season. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Sanitiser price per unit ($) | Chemical cost for the season |
|---|---|
| $2.75 | $736.41 |
| $4.13 | $916.77 |
| $5.5 example above | $1,096 |
| $8.25 | $1,455 |
| $11 | $1,815 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Pool volume
- Choose from Work it out from a rectangular pool, Work it out from a round pool, Work it out from an oval pool, I know the gallons.
- Length (ft)
- A number, between 0 and 300, starting at 32.
- Width (ft)
- A number, between 0 and 300, starting at 16.
- Shallow end depth (ft)
- A number, between 0 and 30, starting at 3.5.
- Deep end depth (ft)
- A number, between 0 and 40, starting at 7.
- Sanitiser
- Choose from Liquid chlorine, Trichlor tablets, Cal hypo granular, Salt system.
- Sanitiser price per unit ($)
- Per gallon, per pound or per bag depending on what you use.
- Sanitiser units per week per 10,000 gallons
- A number, between 0 and 50, starting at 2.5.
- Balancers per month ($)
- Acid or soda ash, alkalinity, calcium and stabiliser.
- Shock and algaecide per month ($)
- A money amount, between 0 and 1000, starting at $28.
- Weeks in the season
- A number, between 1 and 52, starting at 26.
What the results tell you
| Result | What it is |
|---|---|
| Chemical cost for the season | The headline result. A money figure. |
| Pool volume (gallons) | A number. |
| Sanitiser for the season | A money figure. |
| Balancers, shock and algaecide | A money figure. |
| Cost per week | A money figure. |
| Season cost per 10,000 gallons | A money figure. |
Keep going
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