Help & FAQ

For chemistry tools: your pool's volume in gallons and a recent test result for the number you're adjusting (for example free chlorine and CYA for the chlorine calculator). Each tool page lists exactly what to have handy at the top. If you don't know your volume, the pool volume calculator works it out from a few tape-measure readings.

US units by default: gallons, feet and inches, °F, parts per million (ppm), pounds and ounces for dry chemicals, fluid ounces and gallons for liquids, kilowatt-hours and dollars for running costs. Size and dosing tools have a Metric switch, and dose results also show grams, kilograms, milliliters or liters.

Chemical doses and energy costs depend on things a calculator can't see: how fresh your chlorine is, how precisely your test kit reads, the weather, your equipment. So we label those results as estimates and tell you how to verify them, usually by adding about three-quarters of a dose, circulating, and retesting. Results that are straight arithmetic from your measurements say "Calculated" instead.

Stabilizer holds most free chlorine in reserve, so the more CYA your water has, the more free chlorine it needs to sanitize. The calculator uses your CYA to suggest a sensible target range. If you leave it blank it assumes zero, which usually understates what an outdoor pool needs.

Any kit that reports free chlorine (not just total chlorine) works. Drop-based kits are easier to read precisely than strips, and kits that measure free chlorine by counting drops (the FAS-DPD method) stay accurate at the high levels used for shocking.

First the pool volume and its units (gallons vs liters), then the product strength on the label, then your test readings. If it still looks wrong, contact us with the page address: the address already contains the numbers you entered, so we can reproduce it exactly.

Use the Share link button, or just bookmark the page. Calculator inputs are stored in the page address, so anyone who opens the link sees the same numbers and result. The Copy result button copies a plain-text summary plus the link.

No. The calculators run entirely in your browser. Your last pool or hot tub volume and your seasonal checklist ticks are remembered in your browser so other tools can use them; we never receive them. Clearing your browser data removes them.

No. PoolOwl provides general information and estimates for homeowners. Always follow product labels and your equipment manufacturer, and use a licensed professional for electrical, gas or structural work.

Not currently. We don't have relationships with pool companies or chemical brands, and we won't recommend products we can't honestly describe.