Measure first. Plan with confidence.

Aquarium volume calculator

Use this aquarium volume calculator to estimate gallons, liters, water after substrate and how much substrate to buy. Choose a standard tank or enter your own dimensions, then carry that setup into your scape.

How this estimate works

Your tank

Start with what you have

Tank size

Dimensions

Length (in)Width (in)Height (in)

Use label dimensions for an estimate. For a closer measurement, use inside dimensions and your water height.

Substrate depth

Not set

Front (in)Back (in)

Even depth uses the same value at the front and back. Fractions such as 2 1/4 work too.

Enter tank dimensions to use an estimate.

Volume & substrate

Free · No sign-up

Start with your tank

Choose a standard tank or enter length, width and height.

Water estimate

See how much water is left after substrate.

Substrate quantity

Estimate how much to buy for your depth.

Standard aquarium sizes and dimensions

Choose a preset above or compare the library’s dimensions below. Marketed capacity can differ from a rectangular volume calculation.

View standard and brand tank dimensions

Tank	Length (cm)	Width (cm)	Height (cm)
2.5 Gallon	30.5	15.2	20.3
5 Gallon	40.6	20.3	25.4
10 Gallon	50.8	25.4	30.5
15 Gallon	61	30.5	30.5
20 Gallon High	61	30.5	40.6
20 Gallon Long	76.2	30.5	30.5
29 Gallon	76.2	30.5	45.7
40 Gallon Breeder	91.4	45.7	40.6
55 Gallon	121.9	33	53.3
75 Gallon	121.9	45.7	53.3
90 Gallon	121.9	45.7	61
125 Gallon	182.9	45.7	55.9
20C Cube	20	20	20
30C Cube	30	30	30
30F Shallow	30	18	12
36P	36	22	26
45P	45	27	30
45F Shallow	45	24	16
60P	60	30	36
60F Shallow	60	30	18
60H Tall	60	30	45
75P	75	45	45
90P	90	45	45
120P	120	45	45
180P	180	60	60
Fluval Spec V	52	19	29
Fluval Flex 9	34	33	33
Fluval Flex 15	41	39	39
Dennerle Nano Cube 30L	30	30	35
Dennerle Nano Cube 60L	38	38	43
Eheim Aquastyle 35	31	31	36
Juwel Lido 120	61	41	58
Juwel Rio 125	81	36	50
Juwel Rio 180	101	41	50

How the aquarium volume calculator works

Volume to the rim

For a rectangular aquarium, multiply length × width × height in centimeters and divide by 1,000 to get liters. One US liquid gallon equals 3.785411784 liters. This tool uses US gallons, not Imperial gallons.

Estimated water after substrate

The water estimate subtracts substrate volume from the rectangular volume, then reserves 8% for hardscape and space below the rim. This is a planning allowance; measure the actual fill if you need an exact water dose. Glass thickness, equipment, rocks and wood make the real amount different.

Aquarium substrate calculator: depth and quantity

Even substrate depth

Substrate liters = length × width × depth ÷ 1,000. Use the bag’s labeled volume to estimate how many bags you need, then allow for settling and the shape you want. Sand, gravel and aquasoil have different densities. A bag labeled in kilograms needs its product-specific volume or density.

Sloped substrate depth

For a front-to-back slope, use the average: (front depth + back depth) ÷ 2. A 60 × 30 cm footprint with 4 cm in front and 8 cm at the back takes about 10.8 liters of substrate. A central mound or an irregular valley needs a more detailed measurement.

Browse substrate properties and materials before building a plan.

Aquarium volume calculator questions

Why does a standard tank’s label differ from the result?

Marketed capacity is nominal. A rectangular measurement may use exterior dimensions and does not account for the glass, rim, substrate or objects. The calculator displays measured rectangular volume separately from the estimated water you will have after the substrate.

Can I enter fractional inches?

Yes. Use a decimal, a fraction such as 1/2, or a mixed fraction such as 30 1/4. Switch units to see the same dimensions in centimeters. The underlying calculation keeps centimeters for consistency with the planner.

Does the aquarium volume calculator work for curved tanks?

This calculator assumes a rectangular footprint and height. Curved glass, cylinders and irregular shapes need a different formula. Do not use a bounding rectangle as an exact capacity for those tanks.

How deep should my substrate be?

Depth depends on the plants, material and slope. Depth fields start blank. Enter your intended depth, or choose Use a depth estimate after setting your tank dimensions. Try an example loads a sample setup only when you choose it. Check the substrate manufacturer’s instructions and the needs of your plants before buying.

From a calculation to your tank plan

The calculator answers a specific sizing question. In the planner, keep your own choices and place plants, rocks and wood by hand. Review light, CO₂, water conditions and substrate material before requesting an optional analysis.

Read how Scapesome checks a tank · Choose another aquarium calculator