# Spa and Swimming Pool Size Formulas and Calculations

From time to time, a person may need to know a spa or pool
size formula to calculate gallonage for pump run time or
surface area for heating or painting for example. I will
constantly add to this page as more people ask for specific
calculations.

## Gallonage

1)Rectangle: length x width x average depth x 7.5 (liters = meters x 1000)

2)Round: diameter x diameter x average depth x 5.9 (liters = meters x 785)

3)Oval: length x width x average depth x 6.7 (liters = meters x 893)

4)Kidney: average width x length x average depth x 7 = gallons

## Interior Surface of Pool in Square Feet

length x width x 1.6

Believe it or not, this simple formula will work on almost any shape of shell!

## Surface Area of Pool Water in Square Feet

1)Rectangle: length x width

2)Round: radius(1/2 diameter) x radius x 3.14

3)Oval or Roman: 1/2 length x 1/2 width x 3.14

4)Kidney shape: length x width x 0.75

## Amount of D.E. to Add to Filter

AMOUNT OF D.E. TO ADD TO FILTER:

Filter square footage divided by 5 equals number of scoops or 1 pound coffee cans of D.E. to add to skimmer.

## Energy/Cost to Run Pump

ENERGY/COST TO RUN PUMP:

Amps x volts divided by 1000 = kilowatts

Kilowatts x hours per day pump is run x kilowatt hour energy cost = cost per day to run pump.

Note: you may have two amp values listed on your motor;
the higher value is for 115 volts, the lower value 230 volts.
(Because 230 divides the amps between two wires,which puts less stress
on the wiring also)

The link below will take you to pump energy cost
calculator, and also let you compare an average energy efficient
pump to a variable speed pump:

Calculate cost savings with energy efficient pump