Pool & Spa Calculators
26 calculators26 free calculators for pool & spa homeowners.
Water chemistry
How much of each chemical to add to hit your target, and in what order.
Pool Volume
Calculate your pool volume in gallons for rectangular, oval, round, and kidney-shaped pools. Enter length, width, and depth to get an accurate gallon count for chemical dosing.
Chlorine Dosing
Calculate exactly how much chlorine to add to your pool. Enter your pool volume, current and target free chlorine levels, and chlorine product type to get the precise dose.
Pool Shock Treatment
Calculate exactly how much pool shock or bleach you need. Supports HTH, calcium hypochlorite, and liquid chlorine for any pool size (e.g. 12,000 gallons).
Algaecide Dosing
Calculate exactly how much algaecide to add to your pool for weekly prevention, season opening, or an active bloom — with step-by-step guidance for treating green, yellow (mustard), and black algae. Enter your pool volume and algaecide type for the precise dose.
Cyanuric Acid Dosing
Calculate exactly how much cyanuric acid (pool stabilizer) to add to raise CYA to your target level — or how many gallons to drain if CYA is too high. Includes minimum free chlorine guidance.
Pool Alkalinity Dosing
Enter your pool volume and current and target total alkalinity to get the exact dose. Raising takes 1.5 lbs of baking soda per 10,000 gallons per 10 ppm — 6 lbs to go from 60 to 100. Lowering takes acid, and this schedules it in safe rounds so pH does not crash.
Muriatic Acid Dosing
Enter your pool volume, pH reading, and total alkalinity to get the exact muriatic acid dose in fluid ounces. A 15,000-gallon pool at pH 8.0 needs about 17 fl oz to reach 7.5 at 100 ppm alkalinity — but 26 fl oz at 150 ppm. Handles 31.45% and 14.5% acid and dry acid.
Calcium Hardness Dosing
Enter your pool size, surface, and calcium hardness readings to get the calcium chloride dose, split into safe additions, or the share of water to drain and refill when calcium is too high. Uses label rates: 1.25 lbs of flake per 10,000 gallons per 10 ppm, never more than 10 lbs per 10,000 gallons at once.
Pool Salt
Calculate exactly how much salt to add to your pool. Enter your pool volume, current salt level, and target ppm to get the precise weight and number of 40-lb or 50-lb bags needed.
Hot Tub Chemical
Enter your hot tub test strip readings and get how many spoonfuls of chlorine, bromine, pH up or down and baking soda to add, in order.
Equipment, heating and running costs
Sizing the heater and pump, and what the pool costs to run.
Pool Heater Size
Find the right size pool heater in BTU from your pool dimensions, the water temperature you want, and your coldest swim-month air temperature. Sizes gas heaters (150,000–400,000 BTU) and heat pumps (50,000–140,000 BTU) with the Department of Energy method, rounded up to sizes actually sold.
Pool Heating Cost
Calculate exact monthly pool heating costs for gas, electric, or heat pump systems. See seasonal expenses and compare heating methods.
Pool Pump Run Time
Work out how many hours a day to run your pool pump from your pool's gallons and the pump's flow rate, for one turnover in normal conditions, half again as much in hot weather or heavy use, or nonstop when clearing algae. For two-speed and variable-speed pumps, enter your daily high-speed hours and get the low-speed hours that finish the turnover, plus what the mix costs versus running flat out.
Pool Pump Energy Cost
Estimate what your pool pump costs to run per year by type, horsepower, run hours, and electricity rate — and see what a variable-speed pump would cost for the same job, the annual savings, and how fast the upgrade pays for itself.
Pool Filter Replacement Cost
Calculate pool filter cartridge replacement cost — plus sand and DE filters — by pool size. See if your filter is overdue and estimate your 5-year maintenance cost.
Pool Cover Cost
Pool covers run $75 for a winter tarp to $20,000 for an automatic system. Price a first install or replacement by cover type — solar, winter, mesh or solid safety, automatic — plus the cost per year of ownership.
Pool Fill Cost
How much does it cost to fill a pool? Enter gallons or pool dimensions to price the fill — tap vs. delivered water — plus the sewer-fee exemption many utilities give pool fills.
Hot Tub Running Cost
Estimate the yearly cost to run a hot tub or Jacuzzi — electricity, chemicals, water, and filters. Electricity is the big one; see your annual and monthly cost, what drives it, and how a good cover and lower temperature cut the bill.
Spa Electrician Cost
Estimate what an electrician charges to wire a hot tub or spa — the 240V circuit, code-required GFCI disconnect and bonding, wire run, trenching, and a possible panel upgrade. See the cost by run distance, amperage, and whether your panel needs upgrading.
Building, repairing and removing a pool
Installation, resurfacing, liners, decks, and taking a pool out.
Pool Installation Cost Estimator
Estimate what a new swimming pool will cost to install. Compare gunite, fiberglass, vinyl, and above-ground pools by size, add heater, deck, fencing, and more, and see a realistic low-to-high price range.
Pool Liner Replacement Cost
Replacing a pool liner costs $2,000–$5,000 above-ground or $3,000–$7,500 inground, installed. Price your pool size and thickness upgrade — and learn when a $150–$300 patch beats replacing at all.
Pool Resurfacing Cost
Resurfacing a pool costs $6,000–$15,000 for a typical 1,000 sq ft interior — replastering runs $6,000–$8,000, pebble $7,000–$15,000, and full tile up to $30,000. Price your finish and size, refill included.
Fiberglass Pool Repair vs. Reseal
Compare spot-repairing your fiberglass pool's gelcoat damage against resealing (refinishing) the whole interior. See what each costs by pool size and damage extent — and why osmotic blistering means you must resurface, not patch.
Pool Deck Resurfacing Cost Estimator
Estimate pool deck resurfacing costs by material — Kool Deck, concrete overlay, stamped concrete, or pavers. Enter your deck area and condition for an instant project cost range.
Pool Removal Cost
Estimate the cost to remove or fill in an inground pool. Compare partial fill-in vs. full pool demolition by pool size, material, site access, and debris disposal — and see what it costs to fill in a swimming pool.
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About Pool & Spa Calculators
Owning a pool or spa means making expensive decisions with incomplete information. You need to know exactly how much water your pool holds before you can buy chemicals, plan a drain, or understand your water bill. You need accurate calculations for pump sizing, filter capacity, and heating requirements—get these wrong and you'll either waste thousands on oversized equipment or watch your pool stay cloudy and cold.
This calculator hub gives you the math to make those calls confidently, converting your pool's dimensions into the gallonage and flow rates that actually matter for daily operation and maintenance. Beyond the basics, a pool or spa is a long-term investment that requires precise understanding of costs and timelines. You might wonder if it's cheaper to heat with a gas heater or heat pump, how long it really takes to fill your 20,000-gallon spa, or what size pump you actually need to turn over your water properly.
These aren't academic questions—they determine whether you spend $200 or $1,200 annually on heating, and whether you're maintaining a healthy pool or fighting algae blooms. Our calculators handle the conversions and formulas you don't want to get wrong, so you can make decisions based on actual numbers instead of guesses or salesman recommendations.