Pool Salt Calculator
How much salt to add
Use a recent salt test and your equipment’s target. Starting values are examples, not recommended salt levels.
Your pool
Need to measure your pool first? Estimate current gallons from its inside dimensions and waterline
For your target of 3,200 ppm
20 lb owned + 80 lb purchased = 66.763 lb to weigh + 33.237 lb remaining.
Your salt supply
Measurement uncertainty
Your own plausible bounds; not confidence intervals or a dosing guarantee.
Ideal mixing comparison
Discuss options with a pool professional. This comparison does not authorize draining: groundwater, pool structure, liners and discharge rules may make replacement unsafe.
Explore the salt level
A preview changes the comparison, not the target or purchasing plan.
40 lb would bring the nominal reading to 2,879.306 ppm.
Explore a worked example
How to use the result
Use an approved salt product and follow your equipment and pool-surface instructions for adding, circulating and retesting. Confirm volume and reading before acting on a small correction. The calculated mass is not a recommendation to add it all at once. Salt concentration alone does not establish safe swimming water.
Evaporation removes water, not dissolved salt; do not automatically add salt when topping up evaporated water. Splash-out, backwashing and leaks are different.
Purity adjusts the product mass arithmetically; it does not approve additives. The Hayward Salt & Swim 3C manual specifies greater than 99% NaCl and excludes rock salt, iodized salt and anti-caking additives. Follow your own model’s requirements.
Formula, units and limits
For dilute pool water, ppm is approximated as mg/L. Product kg = liters × (target − current ppm) ÷ (1,000,000 × purity fraction). Bags to buy = round up(max(0, required mass − owned mass) ÷ bag mass). Exact input fractions determine purchase boundaries; display rounding never changes the number of bags.
Preview ppm = current ppm + product kg × purity fraction × 1,000,000 ÷ liters. The diagram shows concentration, not water depth. Optional bounds combine supplied volume and reading extremes, treating target and purity as fixed; they are not statistical confidence levels.
Ideal replacement fraction = (current − target) ÷ (current − fill-water ppm). Compared final ppm = current × (1 − fraction) + fill-water ppm × fraction. This assumes one removal from an initially well-mixed pool, refill to its initial volume and complete mixing. It does not model continuous overflow, repeated exchanges or a safe work procedure.
1 US gallon = 3.785411784 L; 1 lb = 0.45359237 kg. Imperial gallons are not supported. Decimal dot or comma, up to 12 decimal places. Arithmetic limits: volume 0.001–1,000,000,000 L; current and fill 0–20,000 ppm; target 0.001–20,000 ppm; purity 99–100%; bag 0.000001–10,000,000 kg; stock and preview 0–1,000,000,000 kg; volume uncertainty 0–50%; reading uncertainty 0–20,000 ppm. These are software limits, not equipment recommendations. Mass displays round to 0.001 of the chosen unit; use a suitable scale.
Sources: Hayward Salt & Swim 3C manual; Pentair IntelliChlor Plus/LT FAQ; NIST unit conversions. Manufacturer targets differ; the example is not universal.
Work out how much pool salt to weigh, how many bags to buy and what remains. Preview salt levels and compare high-salt readings.
