Pond Calculator

Our garden pond calculator is designed with universally accepted mathematical formulas, designed to achieve a balanced system.

Use this calculator to plan your garden pond and realize that your end result may very from the results shown.

I realize that a pond calculator can't answer all your questions but if you use the information provided it will guide you in the right direction.

To start select either the option of a rectangular or square pond and circular or oval pond

Then just enter values in all fields in the pond calculator section.

Please enter all values in feet or with a decimal, do not enter any fractions.

On the reports part of this page you can find the answers to questions such as:

  • liner and underlayment size
  • How many gallons your pond will hold
  • Surface area of your pond
  • Pump size required to turn over or circulate the ponds volume of water per the time you select
  • Filter size required to handle the pump that is required for the turn over rate that you select
  • How many aquatic plants you will need for algae control
  • How many fish your pond will support
  • The waterfall size that works well with the pump size required for the turn over rate that you select

All fields are required to use this pond calculator.

Select Your Pond Type

Rectangular or Square Pond      Circular or Oval Pond

Rectangular or Square Pond

Max. Depth
Average Depth

Now a little more information is needed for this pond calculator.

Overlay (In Feet) This is the amount of liner that is surrounds the pond.

Turnover Rate

Turnover rate is the rate at which your total pond volume is circulated through your ponds filter system. It is a measure of time. Example: 1, 1.5, 2, 2.5, 3 hours. A smaller pond needs a more frequent turnover. A little pond needs at least 1 times per hour, but as the ponds get larger and you have a waterfall that provides good aeration you can get by with less. This works well for a pond with moderate to low fish load, for a heavy fish load use a turnover rate of one regardless of size.

Liner Size

Your pond will require a liner size of: Length X Width

EPDM pond liner is available in widths of 5 ,10 ,15 , 20 , 25 and 30 foot. The length will be cut according to your order.


You will need square foot of underlayment for a liner of this size. To account for waste and overlaps 10% was added.


Your pond will hold US gallons. This is an important number to know. Since your pond is a closed system, the number of gallons that your pond holds will have to be circulated through the filter.

Surface Area

Your pond will have a surface area of square feet.

Surface Area Covered With Aquatic Plants.

You should cover the surface of the pond with aquatic plants like water lily's by 60% and you will need to cover at least square feet with plants, or approximately one for every 10 square foot of surface area that you need to cover.

Water Lilies work great for surface area coverage.

You will need about hardy lilies. A water lily can cover 10 square feet of surface area. Floating aquatic plants such as Hyacinths can also be used to cover the surface area of your pond.

Submerged Plants your pond should contain.

Submerged plants play a valuable role in the garden ponds designs with their diversity and ability to clean the water, removing the excess nutrients that contribute to green water algae. They also oxygenate the pond and sustain your fish and other aquatic wildlife. These plants are a food source for fish and are excellent in protecting the young fish. In this respect alone, they are invaluable to the overall ecology of your pond.

Submerged plants such as Anacharis or Hornwort are sold in bunches so you will need about bunches.

Pump Size

With the pond calculator set to a turnover rate of once every hours. Your pond will require a GPH pump.

Filter Size

With the pond calculator set to a turnover rate of once every hours. Your pond will require a filter that can handle GPH. Please note that the filter size is larger than the pump size by 10% to ensure proper filtration.

Waterfall Size

With the garden ponds designs calculator set to a turnover rate of you should be pumping gallons per hour. This can support a waterfall of inches wide. If you are planning a waterfall for your pond, why not consider a filter falls unit. This type of filter can support a large volume of water and acts as the foundation for your waterfall.

How Many Fish Your Pond Can Support

Stocking level of your pond

Total Inches Of Fish Your Pond Should Support

Koi Fish At 30 Inches In Length.

Comet Goldfish At 14 Inches In Length.

Shubunkin Goldfish At 12 Inches In Length.

The guideline for this is 1 foot of fish for every 24 sq foot of surface area. Koi fish as an adult can grow up to 24-36 inches in length and will uproot or consume plants. It is best to kept Koi in large fish-only ponds. Plants can be put in separate ponds adjacent to the fish pond. Comet goldfish as an adult can grow up to 14 in length. Shubunkin goldfish as an adult can grow up to 12 in length.

It is our hope that this garden pond calculator is helpful to you.

› › Pond Calculator