Pond Unit Converter
Convert the units that matter in pond keeping, instantly as you type. Volume in US gallons, liters, UK gallons, and cubic feet, temperature in Fahrenheit and Celsius, carbonate hardness in dKH and ppm, length in feet and meters, plus pond salt dosing by percentage.
Volume: gallons, liters & UK gallons
1 US gallon = 3.78541 L. 1 UK (imperial) gallon = 4.54609 L. Type in any box.
Cubic feet & US gallons
1 cubic foot = 7.48052 US gallons. Ponds are measured in feet.
Temperature: °F & °C
C = (F - 32) x 5/9. Koi feeding slows below 50 °F (10 °C).
Carbonate hardness: dKH & ppm
1 dKH = 17.86 ppm CaCO3. Aim for ~4 to 8 dKH (70 to 140 ppm) for koi.
Length: feet & meters
1 foot = 0.3048 meters. Useful for metric liner sizes and plans.
Pond salt: target % & pounds per 1,000 gal
0.1% needs about 8.34 lb of salt per 1,000 gallons. Always dose to your real volume.
Test before you dose. Accurate conversions only help if your readings are accurate, so check KH, pH, ammonia, nitrite, and nitrate with a reliable pond test kit, then dose treatments to your true gallons.
Related: pond volume · pond cost · all calculators
The Units Every Pond Keeper Needs
Pond keeping quietly runs on conversions. You measure your pond in feet, dose treatments by gallons, read hardness in dKH or ppm depending on your test kit, follow a koi-care chart that lists temperature in both Fahrenheit and Celsius, and maybe order a liner sized in meters. Getting these conversions right is not just tidiness. Doses of pond salt and medications are calculated against your true water volume, so a slip between US and UK gallons, or a bad cubic-feet-to-gallons step, can mean underdosing a treatment that then fails, or overdosing one that harms your fish. This page keeps the common conversions in one place and updates them live as you type.
US Gallons, UK Gallons, and Liters
The most important volume distinction is US versus UK gallons. A US gallon is about 3.785 liters, while a UK or imperial gallon is larger at about 4.546 liters, roughly 20 percent more. American pond gear and treatments are almost always rated in US gallons, so that is the figure to use unless a product clearly states imperial. When you read a British pond guide or buy equipment imported from the UK, check which gallon they mean before you size a pump or measure out a treatment. The volume converter above moves freely between US gallons, liters, and UK gallons so you never have to guess.
Cubic Feet to Gallons
Because ponds are dug and measured in feet, the cubic-feet-to-gallons conversion is the backbone of pond math. One cubic foot holds 7.48 US gallons. Multiply your pond's length, width, and average depth in feet to get cubic feet, then multiply by 7.48 to reach gallons. A pond that works out to 200 cubic feet holds about 1,496 gallons, enough for a modest koi pond. If your pond is oval, round, or an irregular freeform shape, the simple box formula overstates the volume, so use our pond volume calculator, which applies the right area formula and a shape factor for you.
Temperature, Hardness, and Salt
Temperature drives koi behavior. Their metabolism, appetite, and immune response all rise and fall with the water, so feeding slows below about 50 degrees Fahrenheit, which is 10 Celsius, and stops as they approach winter dormancy. Many koi-care charts print temperatures in both scales, and the converter above flips between them instantly. Carbonate hardness, written as KH, measures the water's buffering capacity, the cushion that keeps pH from crashing. Test kits report it as either dKH or ppm, where one dKH equals about 17.86 ppm of calcium carbonate, and koi do well around 4 to 8 dKH, or roughly 70 to 140 ppm.
Pond salt deserves special care because it is dosed to a target concentration, expressed as a percentage by weight of the water. Common treatment levels sit around 0.1 to 0.3 percent. To reach a target you add a set weight of salt per volume: about 8.34 pounds per 1,000 gallons raises the concentration by 0.1 percent. The salt converter above turns a target percentage into pounds per 1,000 gallons and back, but the dose is only as good as your volume figure, so always work from your real, measured gallons and add salt gradually while watching your fish. When in doubt with a sick or stressed koi, consult a koi or pond specialist rather than guessing.
Keep Your Numbers Consistent
The simplest way to avoid conversion mistakes is to stay in one system per calculation. Measure everything in feet and use 7.48 gallons per cubic foot, or measure everything in meters and use 1,000 liters per cubic meter, but do not mix the two midway. Once you have a reliable volume in US gallons, the rest of pond planning falls into place: sizing a pump and filter, stocking fish, and dosing treatments. Use this converter alongside the volume and cost calculators, and compare specific equipment in our reviews when you are ready to buy.
Keep going: put your numbers to work.
Frequently Asked Questions
What is the difference between US gallons and UK gallons?
They are not the same, and mixing them up is a common pond-dosing mistake. A US gallon is about 3.785 liters, while a UK or imperial gallon is larger at about 4.546 liters, so a UK gallon is roughly 20 percent bigger. Most pond pumps, filters, and treatments sold in the United States are rated in US gallons, while UK products use imperial gallons. Always confirm which gallon your equipment and your medications use, because dosing salt or treatments to the wrong gallon can underdose or overdose your fish.
How do I convert cubic feet to gallons for a pond?
Multiply cubic feet by 7.48052 to get US gallons, since one cubic foot holds 7.48 US gallons. Ponds are almost always measured in feet, so this is the key conversion: work out your pond volume in cubic feet by multiplying length times width times average depth, then multiply by 7.48 to get gallons. For example, 200 cubic feet is about 1,496 gallons. This converter does it instantly, and our pond volume calculator handles odd shapes for you.
What is dKH and how does it relate to ppm?
dKH stands for degrees of carbonate hardness, a measure of the buffering capacity that keeps your pond pH stable. One dKH equals about 17.86 parts per million of calcium carbonate, so a reading of 5 dKH is roughly 89 ppm. Test kits report KH in either unit depending on the brand, which is why converting matters. For koi, a KH of around 4 to 8 dKH, or about 70 to 140 ppm, gives a stable, well-buffered pond that resists sudden pH swings.
Why is pond salt measured as a percentage?
Pond salt is dosed by the target concentration in the water, expressed as a percentage by weight, because that is what actually affects the fish and any parasites. A common treatment level is around 0.1 to 0.3 percent. To hit a target percentage you add a set weight of salt per volume of water: roughly 8.34 pounds of salt per 1,000 gallons raises the concentration by 0.1 percent. Always dose to your real, measured pond volume, and add salt gradually while watching your fish.
How do I convert pond temperature between Fahrenheit and Celsius?
To go from Fahrenheit to Celsius, subtract 32 and multiply by 5/9. To go the other way, multiply Celsius by 9/5 and add 32. Temperature matters in a pond because koi metabolism, feeding, and immune response all change with it: koi feeding slows below about 50 degrees Fahrenheit, or 10 Celsius, and you stop feeding entirely as they approach winter dormancy. Many koi-care charts list temperatures in both units, so a quick conversion helps you read them correctly.
Why convert feet to meters for a pond?
US pond builders measure in feet, but liners, plans, and many product specs from Europe and Asia use meters. One foot equals 0.3048 meters, so a 12-foot pond is about 3.66 meters. Converting helps when you order an EPDM liner sized in metric, follow an overseas build guide, or compare equipment specs. For volume work, stay consistent: measure everything in feet and use 7.48 gallons per cubic foot, or measure in meters and use 1,000 liters per cubic meter.