Aquarium Calculator
How many gallons or litres a rectangular fish tank holds, what the water weighs, and with the glass thickness, what the glass and the full tank weigh.
Result
Buy 56.7 gal
Filled to the brim. Gravel, rock and decorations take up room and add weight of their own.
- Weight of the water
- 473.4 lb (214.7 kg)Estimate
https://calcgallery.com/area-volume/aquarium-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use the Aquarium Calculator
- Measure the tank's length, its width from front to back and its height, on the outside.
- Enter the glass thickness if you know it. It is optional.
- Read how many gallons or litres the tank holds and what the water weighs.
- With the glass thickness, also read what the glass and the full tank weigh.
How it is calculated
inside = (length − 2 × glass) × (width − 2 × glass) × (height − glass)water = inside × density of waterglass = (length × width × height − inside) × density of glasstotal = water + glassThe inside is an open-topped box: the front, back and two ends each take one glass thickness off the length and width, and the bottom takes one off the height. Water is taken as 1,000 kg per cubic metre. The glass is soda lime float glass at 2,500 kg per cubic metre (156 lb per cubic foot), the figure in Guardian Glass’s float glass technical note.
What it leaves out
The weight is water and glass only. Substrate, rock, the lid, the lighting, the stand and any trim are extra, and a rimmed or braced tank has more glass than five plain panes. Whether a stand or a floor can carry the load is a structural question; the page does not answer it.
With your numbers
- Volume = length × width × height, inside the glass = 51.68 gal
- Water = 51.68 gal × density of water = 431.3 lb
- Glass = volume of the five panes × density of float glass = 105.3 lb
Quick reference
Filled to the brim. Gravel, rock and decorations take up room and add weight of their own.
| Job | Water volume, filled to the top |
|---|---|
| 48 × 13 × 21 in, 3/8 in glass | 51.7 gal |
| 24 × 12 × 16 in, 1/4 in glass | 18.4 gal |
| 30 × 12 × 18 in, inside sizes | 28.1 gal |
| 36 × 18 × 24 in, 1/2 in glass | 60.5 gal |
| 72 × 18 × 24 in, 1/2 in glass | 122.8 gal |
| 120 × 40 × 50 cm, 10 mm glass | 219.7 L |
| 60 × 30 × 36 cm, 6 mm glass | 59.9 L |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
2 sources
NIST Chemistry WebBook, water at 4 °C and 0.101325 MPa: 999.9749 kg/m³ (IAPWS-95), https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185, rounded to the conventional 1000 kg/m³ of NIST SP 811 (2008) Appendix B, centimeter of water, conventional = 98.0665 Pa.
Used for
- The conventional density of water, 1000 kg/m³. Pure water at 4 °C, its densest, is 999.97 kg/m³.
Guardian Glass, Expert Series: Manufacturing Process for Float Glass, v.8.2020-es-mpfg, table "Mechanical And Physical Properties of Soda Lime Float Glass": "Density 156 lbs/ft3 2,500 kg/m3". https://www.guardianglass.com/content/dam/guardianindustriesholdings/collateral/usca/brochure_expert_series_EN_doc5_mfg_process_float_glass_2020.pdf
Used for
- Density of soda lime float glass, the glass of an ordinary aquarium: 2,500 kg/m³ (156 lb/ft³).
Common questions about the Aquarium Calculator
- How many gallons is my fish tank?
- Multiply length, width and height in inches and divide by 231, the cubic inches in a US gallon. A tank 48 by 13 by 21 inches on the outside is 56.7 gallons of box, but with 3/8 inch glass the space inside is 51.7 gallons, which is why the thickness makes a difference.
- How much does a filled aquarium weigh?
- Water is about 8.3 pounds a US gallon, a kilogram a litre. A tank 48 by 13 by 21 inches with 3/8 inch glass holds about 431 pounds of water, and its glass adds about 105 pounds, before any gravel, rock, lid or light.
- How thick should the glass be?
- This page does not say. Glass thickness depends on the height of the water, the length of each pane, the glass type and how it is supported, and getting it wrong is a safety matter. Follow the tank maker, or a design method for aquarium glass from a qualified source.
- Why is my real volume lower than this?
- Few tanks are filled to the brim, and gravel, rock, plants and equipment all take up space. Filling a 48 by 13 inch tank with 3/8 inch glass to 1 inch below the top holds about 2.5 gallons less. Gravel holds some water between its stones, so it takes out less than its own volume.