Calculators - Further Reading

Calculators for Pool Design and Maintenance

At TFP we believe pool maintenance should be based on science and physics. There are many underlying calculations that go into TFP recommendations and advice. Below are some tools to allow you to make your own calculations and see the effects on your pool.

Pool Math

Pool Math makes it simple to track all of your Pool Test Logs and takes all of the guess work out of how much chemical you need to add.

Pool Math calculates the quantities of chemicals required for adjusting chlorine, pH, alkalinity, calcium, CYA, salt, and borates. It also calculates the Calcium Saturation Index if you log the water temperature.

You need to enable tracking of CSI, salt, borates or water temperature under the round hamburger option icon.

Pool Math also calculates the effects of adding a chemical and calculates the normalized price of bleach/chlorine so you can compare the value of products with different chlorine percentages and quantities.

The Effects of Adding Chemicals in Pool Math includes a SWG run time calculator to calculate the FC output for a given % and run time of salt water chlorine generators. You go to Effects of Adding Chemicals; Select SWG; Select which SWG you have; Put in % setting and pump run time and it will show you the FC generated per 24 hours.

Pool Water Evaporation Rates

This Water Evaporation spreadsheet will calculate the evaporation rate given air and water temperature, relative humidity, and wind. Note that this is the wind speed at the surface of the water which is usually quite a bit lower than general wind speed due to fences and the water being somewhat below ground level.[1]

The Evaporation Estimator provides the estimated evaporation rate from these variables for a particular pool on a particular day. You enter your zip code to automatically populate the current weather related information for your area. You can also enter weather related variables if you wish. Pool related variables are automatically populated with “typical” values although these also can be changed to best represent a particular pool.

For more read Evaporation of Pool Water.

Lowering Chlorine Quickly

If you need to lower chlorine quickly then read How Can Free Chlorine be Lowered in Pool Water?

The sodium thiosulfate calculator on – enter your pool size in gallons (or liters) and the current chlorine level in ppm, and it tells you how many ounces or grams of Sodium Thiosulfate to add to reduce chlorine to zero.

Pool Heating

Heater Run Time and Cost Calculator

This Heating Runtime and Cost spreadsheet[2] contains:

  • A Scratch Pad where you can estimate the hours needed to run the heater to achieve a desired temperature rise for a given water volume. There is a Multiplier Factor to account for variability in heating water that is subject to the elements. This is explained further in the spreadsheet.
  • A Cost Estimator where you can select the billing unit from a drop-down list, cost per billing unit, heater BTU, and number of hours the heater is run. For the number of hours, you can use either the hours calculated in the Scratch Pad or enter your own figure. The spreadsheet calculates cost by taking the cost per billing unit and dividing it by the number of BTUs in that billing unit to arrive at a cost per BTU. It then takes the cost per BTU and multiplies that by the Gross BTU output of the heater to get the cost per hour to run the heater. The cost per hour is then multiplied by the number of hours the heater is run to arrive at the Total cost to run the heater for X hours.

The spreadsheet is set up to use with Natural Gas heaters. It estimates the variable usage-based cost that appears on your bill. Fixed costs that appear on your bill are not factored into cost calculations since, by definition, a fixed cost is static and would appear on your bill as the same amount each month regardless of consumption.

When using the runtime for Heat Pumps put the Heat Pump BTU's in the Net heater BTU field instead of reducing it by 20% for natural gas heater efficiency loss.

For calculating heat pump costs vendors like Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location.

This spreadsheet loads in Excel .xls 2003 format but should be saved in .xlsx format.

Natural Gas Heating Cost Calculator

3-27-2020 This link is getting DATABASE CONNECTION ERRORS but I am not deleting it hoping they will get their site running.

The thermodynamics of heated and non heated swimming pools is quite complicated. This Swimming Pool Energy and Temperature Calculator from Neil O. Anderson & Associates makes it easy for pool builders and designers to predict the amount of energy needed to heat a pool, or to calculate the temperature of a pool at a given time during the year.

The calculator uses geographic data combined with solar and wind data to accurately calculate thermal parameters. The program also incorporates pool features such as pool covers, insulation, and wind breaks. The program output shows you cost by month to see how your monthly temperature changes affect cost.

Raypak Gas Pool Heater Sizer

Raypak has a Gas Pool Heater Sizer. It tells you the Temperature Rise/Hr and Natural Gas and Propane costs to heat a pool in your local area to selected temperature by month. Adjust the natural gas cost and propane cost in the lower left to your local gas prices for accurate costs.

Pentair Heat Pump Calculator

Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source.

To get the most accurate cost comparison you should change the default electric kwh, natural gas price, and propane price to actual prices in your area.

Water Heating Calculator for Time, Energy, and Power

Water Heating Calculator for Time, Energy, and Power computes how long it takes to heat water, how much energy is consumed, and how much heating power is required.

The calculators support Celcius/Centigrade, Fahrenheit, Watts (w), Kilowatts (Kw), Btuh, Joule, British termal unit (Btu), liter, gallon, kg, lb, cubic inch, cubic foot etc.

The calculators assume 100% efficiency and no loss of energy during the heating process.

Estimating Pool Water Gallons

If you need to get an estimate of the amount of water in your pool you can use the calculator at the bottom of the old Pool math web page. You simply enter the pool dimensions and average depth and it gives you the gallons of water in the pool.

Pentair has a Pool Volume Calculator that lets you select from rectangular, oblong, round, and triangle shapes.

There is also a Chemical Way of Calculating Pool Volume using an alkalinity test kit, sodium bicarbonate or acid, and the formula.

Irregular Pool Shape Area Calculator

Area of Polygon by Drawing is a neat website for plotting all those Freeform pools.[3] The default shape on the graph is a pentagon but you can add points by pressing the up arrow and I got bored pressing it well after making a 100+ sided shape. If you zoom out on the graph you can make your Freeform pool shape with just a few measurements and round off all the extra points.

The area is shown up top at all times and multiply it by the average depth for cubic feet. Multiply that by 7.481 gallons per cf and it should be pretty accurate.

Hydraulics 101 - Pump and Pool Spreadsheet Tools

@mas985 has developed the following spreadsheets:

  • Pool Pump Tools - Estimates pump operating points, pump energy costs and waterfall flow rates.
  • Pool Heat Transfer Tools - Estimates heat loss and gain from a full heat transfer model that includes the effects of the sun, solar panels, NG heater, heat pump, and environmental conditions. It will also estimate the amount of water lost per day/week due to evaporation. Included are tabs to estimate heat loss from pipes and how long it can take for a pipe to freeze.
  • Chemistry Calculator - Calculate chemicals required to balance pool chemistry and logs test results.

License agreement and download links can be found at the Hydraulics 101 thread.

SWG Runtime Spreadsheet

SWG Runtime Spreadsheet .png

While the PoolMath App will calculate SWG runtime and FC output, you will find the link to the SWG Runtime Calculator in the first message of the thread if you prefer a spreadsheet to the App.

You need to know the 24 hour FC output of your SWG cell at 100% to enter into the spreadsheet and the PoolMath App has a lookup for that.

Stenner Pumps

Stenner Pump Calculator (Excel)

The Stenner Pump Calculator determines the chlorine dosing required each day, It calculates the volume of liquid chlorine needed each day and the time required to run the pump to achieve the required chlorine dose.

You need to know the flow of your pump, your pool volume, liquid chlorine concentration and the target chlorine level you want to obtain.

Stenner Pump Runtime and Usage Spreadsheet

The Stenner calcs spreadsheet gives you spreadsheets to calculate run time and usage. The Usage spreadsheet will track your usage, and will help you know when to go fill the tank.

Stenner calculator setup & tracking

Another stenner calculator setup & tracking Excel spreadsheet from @gp2.

VS Pump Energy Cost Comparison


Check your electric bill and use the fully loaded kWh cost including any transmission or distribution system fees.

Plaster and Grout Coverage

SGM has calculators to determine the bags of plaster needed for a pool and the coverage a 25 lb of grout will give you.

How Much Gravel Will You Need?

Try some of these calculators: