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Methodology

The formulas and assumptions behind every calculator.

This page keeps the calculator methods in one place. It is meant for auditing, not for replacing product labels, equipment manuals, local rules, or professional advice when pool water is unsafe or unstable.

Last reviewed July 7, 2026

Pool Salt Calculator

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Formula used Pool gallons x ppm increase x 0.00000834 = pounds of salt

Assumptions

  • The ppm increase is target salt ppm minus current salt ppm. If current ppm is higher than target, the calculator switches to dilution guidance.
  • Bag count rounds up for shopping because pool salt is usually sold by the full bag.
  • A generic target such as 3200 ppm should be replaced by the target range in the saltwater chlorine generator manual.

References checked

Last reviewed July 7, 2026

Pool Chlorine Calculator

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Formula used Pool gallons x ppm increase x 0.00000834 / product strength = product pounds

Assumptions

  • For liquid products, product pounds are converted to approximate gallons using 8.34 pounds per gallon.
  • The calculator handles immediate chlorine additions. Slow-dissolving tablets are not a fast ppm correction.
  • If current free chlorine is already above target, the dose is zero and retesting is the next step.

References checked

Last reviewed July 7, 2026

Pool pH Calculator

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Formula used Per 10,000 gal: about 12 fl oz muriatic acid lowers pH 0.2, or 6 oz soda ash raises pH 0.2

Assumptions

  • pH adjustment is not perfectly linear. Total alkalinity, borates, temperature, aeration, and test accuracy can change the real dose.
  • This page intentionally supports only two products with clear planning factors: 31.45% muriatic acid and soda ash.
  • The calculator caps the first dose so large changes are handled in stages and checked by retesting.

References checked

Last reviewed July 7, 2026

Pool Alkalinity Calculator

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Formula used Raise TA: gallons / 10,000 x ppm increase / 10 x 1.5 lb baking soda. Lower TA staged acid need: gallons / 10,000 x ppm decrease / 10 x 25.6 fl oz muriatic acid

Assumptions

  • The baking soda estimate uses a common planning rule of 1.5 lb per 10,000 gallons for each 10 ppm TA increase.
  • Lowering total alkalinity is not a one-step chemical add. Acid lowers pH and TA, then aeration helps pH recover.
  • The acid result is a staged planning amount, not a one-pour dose. Large alkalinity moves should be split with pH and TA retesting.

References checked

Last reviewed July 7, 2026

Pool Stabilizer Calculator

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Formula used Dry CYA pounds = pool gallons x ppm increase x 0.00000834 / product strength. Dilution fraction = 1 - target CYA / current CYA

Assumptions

  • The dose assumes dry cyanuric acid. Liquid conditioner products vary by concentration and should follow the product label.
  • If current CYA is above target, the calculator switches to dilution guidance instead of recommending more stabilizer.
  • CYA can dissolve and show on tests slowly, so large corrections should be staged and retested.

References checked

  • Florida DEP water formulas Public operator formula sheet that includes pounds, dose, flow, and 8.34 water-treatment relationships.
  • Pool chemistry adjustment guide Public-health pool adjustment table for pH, alkalinity, and staged dosing.
  • CDC Model Aquatic Health Code Public pool health-code context for cyanuric acid, stabilized chlorine, and the way CYA changes chlorine effectiveness; useful for safety framing but not a residential pool rulebook.

Last reviewed July 7, 2026

Pool Volume Calculator

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Formula used Cubic feet of water x 7.48 = US gallons

Assumptions

  • Average depth is used for sloped pools because most pool chemical labels dose from estimated total water volume.
  • Round and oval pools use geometric surface-area formulas, so steps, ledges, spas, and freeform areas should be estimated separately when they are large.
  • The 8-hour turnover estimate divides gallons by 480 minutes and does not replace pump curve or plumbing calculations.

References checked

Last reviewed July 8, 2026

Pool Pump Size Calculator

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Formula used Required GPM = pool gallons / turnover hours / 60

Assumptions

  • The result is a turnover planning flow, not an exact horsepower recommendation.
  • Final pump selection depends on pump curve, total dynamic head, plumbing layout, filter rating, heater flow, electrical requirements, and local code.
  • Filter maximum flow can limit the practical target. If required GPM exceeds the filter rating, a longer runtime or equipment review is needed.

References checked

Last reviewed July 8, 2026

Pool Heating Cost Calculator

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Formula used BTU needed = pool gallons x 8.34 x temperature rise °F

Assumptions

  • This estimates heat-up energy, fuel use, and runtime from user-entered assumptions. It is not an exact monthly heating bill.
  • Heat pump COP, gas heater efficiency, propane heater efficiency, and electric price must be checked against local utility rates and equipment documentation.
  • Maintaining temperature depends on weather, wind, humidity, sunlight, evaporation, cover use, heater condition, and runtime strategy.

References checked

Last reviewed July 12, 2026

Pool Shock Calculator

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Formula used Pool gallons x ppm chlorine increase x 0.00000834 / product strength = product pounds

Assumptions

  • Liquid chlorine is converted from pounds to approximate gallons using 8.34 pounds per gallon as a planning shortcut.
  • Automatic CYA-based targets are limited to the published residential FC/CYA planning values from 20 through 80 ppm CYA. Below or above that range, enter the target from the method, product label, or equipment guidance you are using.
  • Old liquid chlorine may be weaker than its label strength, so dose conservatively and retest.

References checked

  • Florida DEP water formulas Public operator formula sheet that includes pounds, dose, flow, and 8.34 water-treatment relationships.
  • CDC pool chemical safety Storage, handling, and mixing precautions for pool chemicals.
  • CDC healthy swimming General public-health context for recreational water and swimmer safety.
  • Trouble Free Pool FC/CYA Chart Published residential FC/CYA planning chart used for the exact automatic shock targets from 20 through 80 ppm CYA; it is a community methodology, not CDC guidance, a code, or a product label.

Constant-by-constant sources

  • CYA 20-80 ppm -> FC 10-31 ppm The automatic table uses the source chart values: 20 -> 10, 30 -> 12, 40 -> 16, 50 -> 20, 60 -> 24, 70 -> 28, and 80 -> 31 ppm FC. Relationship: direct residential planning method. Trouble Free Pool FC/CYA Chart
  • CYA below 20 ppm or above 80 ppm The calculator intentionally does not extrapolate the table. Enter the target specified by the method, label, equipment, or local guidance you are using. Relationship: manual target required.