Pool calculators that show their work
By Marko Visic, BSc Physics, MPharm Updated Oct 25, 2026Cloudy water, chlorine that won't hold, a salt system you're not sure how to size, a heating bill that stings. Whatever brought you here, there's a calculator that solves it exactly and shows you why. No chemistry degree required.
The calculators to start with.
Pick the one closest to what you came here to solve. Each shows the math step by step so you can see why the number is right. No chemistry degree required.
Pool Volume Calculator
How many gallons is your pool? Start here: everything else needs it.
Open the calculator →Salt Chlorine Generator Calculator
What size salt system you need, and why the box rating lies.
Open the calculator →Pool Chlorine Calculator
Exactly how much chlorine to add, for your stabilizer level.
Open the calculator →Pool Heating Cost Calculator
What your pool really costs to heat, and how much a cover saves.
Open the calculator →Pool Pump Run Time Calculator
Stop overpaying to run your pump: find the real run time.
Open the calculator →Pool LSI Calculator
Is your water about to corrode your equipment or scale it up? One number tells you.
Open the calculator →
How the calculators fit together
Solve one — the related ones are right next to it.
All 22 calculators on this site connect. Your gallons feed every chemistry dose, every heating BTU, and every filtration setting; the chemistry numbers roll up into one water-balance verdict; the filtration calculators share a single chain. So whichever calculator you came here for, the related ones you'll need next are right next door.
Volume drives everything
Every chemistry dose, every heating bill, every filtration setting starts from your gallons. Get the volume wrong by 10% and every downstream number is wrong by 10%, so the volume calculator is the natural starting point.
Water balance ties chemistry together
pH, alkalinity, calcium, temperature, and stabilizer aren't separate problems. One number combines them and tells you whether your water is balanced, corroding your equipment, or building up scale. That number lives on the water-balance calculator.
Filtration is one chain
Required flow → the right pump → the right filter → the monthly cost. Four calculators on one chain, and it's easy to end up oversized in a way that quietly costs more every month. Start from pump run time.
The full inventory
All 22 calculators + 1 maintenance guide
Grouped by topic, in the logical order an owner usually wants them. Each entry tells you exactly what it answers; click through to the calculator that owns the number.
Pool Chemistry
11 calculators · 1 guide
Pool Volume Calculator
Gallons or liters for any pool shape: rectangle, round, oval, kidney, L-shape, diving pool. Every other chemical, salt, and heater decision on the site starts from this number.
Pool Salt Calculator
Pounds, 40-lb bags, or kilograms to hit your generator's target ppm, with brand presets from Intex, Hayward, and Pentair and the 'add 80% first' rule when the reading is uncertain.
Salt Chlorine Generator Calculator
What size salt cell you actually need, from your demand AND your pump hours, matched to sourced Pentair IntelliChlor and Hayward TurboCell ratings. The catch: the box rating assumes 24-hour pumping, so on a normal 12-hour schedule the cell rated for your gallons can't keep up. Size for your hours, not the label.
Saltwater Pool Conversion Cost Calculator
What converting a chlorine pool to saltwater actually costs: itemized SWG unit (sized to your pool) + salt charge (in lbs and bags) + install (DIY or pro), plus a payback estimate by your current chlorine spend. The part to plan for: a salt cell wears out every ~5 years, so saltwater is cheaper chlorine, not free chlorine; a heavy spender recoups in ~2 yr, a light user may never.
Pool Chlorine Calculator
Exact dose for liquid, trichlor, dichlor, or cal-hypo, with the FC target your CYA actually demands (not a flat 3 ppm), plus the side-effect ledger every product adds.
Cyanuric Acid Calculator
Raise CYA with stabilizer dose for your gallons, or lower a runaway reading with a verified partial-drain plan. Five brand presets and the FC-cost ledger every CYA target carries.
Pool pH Calculator
Muriatic acid or dry acid to drop pH and TA together; soda ash to raise pH. With the CO₂-driven pH bounce-back explained: it isn't your dosing.
Pool Alkalinity Calculator
Baking soda to raise TA; acid + aeration to lower it without crashing pH. Matched to the pH calculator: identical inputs return identical acid doses on both pages.
Pool Calcium Hardness Calculator
Calcium chloride dose with the assay-grade gap disclosed: anhydrous 94–97% vs flake 83–87% or 77–80%, each dosed on its own CaCl₂ assay, not averaged. Dilution math for when CH needs to come down, because no chemical lowers calcium.
Pool LSI Calculator
Langelier Saturation Index from the full continuous saturation equation, with the cyanurate correction that turns a 'balanced' verdict into 'corrosive' when CYA is in the mix.
Pool Shock Calculator
Breakpoint target at 10× combined chlorine to clear chloramines, or a superchlorinate level you set by the product label, not a CYA-keyed formula. With the no-chlorine-floor case (drain, don't dose).
Pool Heating
4 calculators
Pool Heater Size Calculator
BTU sizing with the two-number method (volume heats, surface area loses) and the cover that's the strongest single lever against standing loss. A class range, never fake-precision.
Pool Heating Cost Calculator
Heat-up + monthly maintenance cost across gas, propane, heat pump, and electric resistance. The headline: on a typical gas-heated pool a cover pays for itself in days, not months.
Pool Evaporation Calculator
Vapor-pressure physics tied to your weather and humidity gives gallons-per-day and a leak-or-evaporation verdict. A cover cuts evaporation by ~90%, the same lever that dominates heating cost.
Pool Heat-Up Time Calculator
Time to target with the real climb, well past the rule-of-thumb estimate, because the pool sheds heat while it warms. Reverse mode answers 'warm by Saturday?' planning questions.
Pool Pump & Filter
4 calculators
Pool Pump Run Time Calculator
Real turnover hours with the two facts the conventional advice misses: one turnover filters ~63 % (not 100 %, the 1 − e⁻ⁿ exponential mixing law), and the cube law makes slow-and-long dramatically cheaper than fast-and-short.
Pool Pump Size Calculator
Operating point solved by bisection root-finding: the flow you'll actually get, not the nameplate. A bigger pump barely helps; a bigger PIPE wins, giving more real flow for less power.
Pool Filter Size Calculator
Bigger filter is genuinely better: more area, slower rate, finer particle capture, longer cycles. The detail that matters: the 48× area spread between sand and cartridge at the same flow, both correctly sized.
Pool Pump Cost Calculator
What your pump actually costs to run, and why the real variable-speed saving lands inside DOE's 50–75 % range rather than a single headline number: real friction follows flow^1.852, not flow³, and static head doesn't scale.
Pool Water & Filling
3 calculators
Cost to Fill a Pool
What it actually costs to fill your pool, plus the sewer-exemption saving that's easy to miss. Pool fill water doesn't enter the sewer, so many utilities waive the sewer charge if you ask.
Pool Fill Time Calculator
How long it takes: longer than you'd expect on a typical garden hose. With the bucket test (gpm = 300 ÷ seconds for a 5-gallon bucket) so the estimate is built on your hose, not an average.
Round Pool Gallons
The real manufacturer-published gallons for common Intex/Bestway round above-ground pools (by diameter and wall height), because a 52″ pool holds water to ~45″, not 52″, and the same nominal size differs by brand. Sourced chart + measure-it fallback.
Trust & methodology
Why you can trust these numbers.
You've seen what the site solves above. The rigor underneath is simple: every constant on PoolSolver traces to a named primary source, every formula is derived in plain language on the page that uses it, and the dual credential maps to the specific calculator domains it covers.
The verified-or-omitted standard. Every number on PoolSolver traces to a primary source, or it isn't published. No fabricated figures, no rounded shortcuts that quietly become wrong (the difference between 7.48052 gal/ft³ and a rounded 7.5 is a 0.26% volume error that propagates into every downstream calculation), no “studies show” without citations.
The primary sources, by name.
- NIST for physical constants: 1 mg/L in one US gallon = 8.3454 × 10⁻⁶ lb, an exact unit conversion (NIST Handbook 44: 1 gal = 231 in³, 1 lb = 0.45359237 kg), and the 7.48052 gal/ft³ conversion anchor every volume and chemistry calculation on the site. Molecular weights are IUPAC 2024 standard atomic weights (CIAAW).
- The CDC's Model Aquatic Health Code (MAHC) for water-chemistry operating ranges: the 7.0–7.8 pH operating range (MAHC 2024, 5th ed., §5.7.3.4.1) is the standard the chemistry calculators reference; MAHC governs public pools and contains no saltwater-specific provisions, which the saltwater pages state plainly.
- Manufacturer install guides and spec sheets for equipment: Pentair IntelliChlor and Hayward TurboCell cell output ratings (the 24-hour-pump-runtime correction); Intex and Bestway published water capacities for round above-ground pools (we cite per row, with the fill convention stated).
- APHA Standard Methods for the Examination of Water and Wastewater for the alkalinity titration and CaCO₃-equivalent basis behind the dosing math (reused across salt, chlorine, calcium, CYA, alkalinity, and pH calculators). Here ppm means mg/L, as in the MAHC and pool test kits.
Show the work. Every calculator exposes its intermediate steps (the substitutions, the units, the constants) so the result is auditable, not a black box. Two concrete examples: the salt calculator showslb of salt = ppm-shift × gallons × 8.345 × 10⁻⁶with each substituted value visible in a step table; the LSI calculator renders the carbonate-alkalinity correctionTA − CYA × cyanurate-factor(pH) so you see exactly how high CYA flips a “balanced” verdict to “corrosive”.
The author. Marko Visic, BSc Physics, MPharm: BSc Physics, Faculty of Mathematics and Physics, University of Ljubljana, Slovenia; Master of Pharmacy (MPharm), Faculty of Pharmacy, University of Ljubljana, Slovenia. The physics credential applies to the volume, hydraulics, and thermal calculators (NIST constants, ASHRAE heat-loss conventions, the cube-law pump physics); the pharmacy/chemistry credential applies to the dosing math (APHA-derived ppm), the LSI water-balance calculation, and the saltwater electrochemistry (electrolysis at the cell, galvanic corrosion between dissimilar pool metals). The credential is the basis for categorizing claims on pages like the saltwater maintenance hub where mechanism, standard, and industry practice are labeled distinctly. About the author.
CC BY 4.0 datasets. The site's sourced reference tables (manufacturer salt-cell ratings, the saltwater galvanic series for pool metals, round-above-ground stock-size capacities) are released under CC BY 4.0 so other authors can reuse them with attribution. The sourced tables are the site's original contribution; the calculators render them, never invent them.
Frequently asked questions
- What pool calculator do I need?
Start with the pool volume calculator. Volume is what every other pool decision builds on: every chemistry dose, every heating BTU, every filtration turnover starts from your gallons. One wrong volume number propagates into every chemical and equipment calculation, so get that right first. From there, the system view above routes you to whatever you're trying to solve.
- Are these pool calculators accurate?
Every number on this site traces to a primary source: NIST for physical constants (the exact 8.3454 × 10⁻⁶ lb per mg/L·gallon unit conversion from NIST Handbook 44, the 7.48052 gal/ft³ conversion), IUPAC/CIAAW for molecular weights, the CDC's Model Aquatic Health Code for chemistry operating ranges, manufacturer install guides for equipment specs (Pentair IntelliChlor and Hayward TurboCell ratings, etc.). The verified or omitted standard means: if a number can't be sourced, it's not published. Every calculator shows its work step by step so the result is auditable, not a black box.
- How do I calculate my pool's volume?
Use the pool volume calculator. It handles seven pool shapes (rectangle, round, oval, true ellipse, kidney, L-shape, diving pool with hopper) and shows the math: surface area × average depth × 7.48052 gal/ft³ (the NIST-exact conversion). For round above-ground pools specifically (Intex and Bestway), the round-pool-gallons page has the manufacturer-published water capacity already verified, typically more accurate than the geometric formula because it accounts for the real water line (a 52-inch wall pool holds water to ~45 inches).
- What's the most important pool calculation?
Volume. Nearly everything else scales from it: chlorine and salt doses scale linearly with gallons (ppm × gallons × 8.345 × 1e-6 = lb of chemical); heating BTU and heat-up time scale with gallons × specific heat × temperature rise; filtration turnover is gallons divided by flow rate. A 10% volume error compounds into a 10% chemistry error, a 10% heating cost error, and a 10% filtration sizing error, all from one wrong number at the top.
- Do you cover saltwater pools?
Yes. The salt calculators cover it end-to-end. The pool salt calculator computes the salt dose to your generator's target ppm; the salt chlorine generator calculator picks the right cell from sourced Pentair/Hayward ratings (and corrects the catch: cell outputs are 24-hour-pump ratings, so on a normal 12-hour schedule you get half); the saltwater pool conversion cost calculator totals what a chlorine-to-salt switch costs with a payback estimate (cheaper chlorine, not free chlorine: the cell wears out after about 10,000 operating hours, roughly 3–5 seasons). And the saltwater pool maintenance page ties them together with a personalized schedule + the sourced saltwater galvanic series for pool metals.
- What makes PoolSolver different?
Three things, in order of importance. (1) The system view: the calculators are a dependency graph, not a grid. Volume feeds everything, LSI combines the chemistry parameters into one number, turnover drives the filtration chain. Other pool-calculator sites present a flat list; we present the structure. (2) Primary sourcing: every constant traces to NIST, IUPAC, USGS, MAHC, or a named manufacturer spec, with no rounded shortcuts and no “studies show” without citation. (3) Show the work: every calculator exposes its steps so you can audit the answer, written by an author with a BSc in Physics and an MPharm, the credential applied to the calculator domain it covers.