Aquarium Substrate Calculator
Estimate uniform aquarium-substrate volume and mass from tank-bottom dimensions.
Open toolAquarium Volume Calculator
Enter your tank's interior length, width, water fill height, and hardscape displacement in the Aquarium Volume Calculator below to find gross and net water capacity in US gallons and liters plus filled water weight.
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Enter the inputs, then select Calculate Tank Volume.
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How Aquarium Volume Calculator works
The Aquarium Volume Calculator computes interior cubic volume for rectangular, cylindrical, or bowfront tanks, converts cubic inches (divided by 231) or cubic centimeters (divided by 1,000) into gallons and liters, and deducts your substrate displacement percentage.
Gross US Gal = (L_in * W_in * H_in) / 231; Net Water = Gross * (1 - Displacement% / 100); Water Weight = Net Liters * 1.0 kg.
Also outputs surface area (L * W) for gas-exchange assessment and recommended weekly 25% water change volume.
Aquarium Volume Calculator Quick Reference & Input Guide
Review the input parameters, allowed value ranges, and worked reference cases for the Aquarium Volume Calculator below before running your calculation.
| Parameter / Scenario | Default / Sample Value | Rule or Allowed Range | Output / Usage Note |
|---|---|---|---|
| Input: Dimension unit | in | Options: Inches (in), Centimeters (cm) | Required workspace parameter |
| Input: Aquarium shape | rectangular | Options: Rectangular / Cube, Cylinder (Length = Diameter), Bowfront (Width = Side Width, +25% center bow) | Required workspace parameter |
| Input: Interior length (or cylinder diameter) | 48 | Range: 1 to 1000 | Required workspace parameter |
| Input: Interior width (front to back) | 18 | Range: 1 to 1000 | Required workspace parameter |
| Worked Case 1: Standard 75-gallon footprint (48 x 18 x 20 in water height, 10% displacement) | Preloaded / test values | Rectangular Volume = L * W * H; US Gallons = Cubic Inches / 231; Liters = Cubic Centimeters / 1000; Net Volume = Gross Volume * (1 - Displacement% / 100) | Interior water volume is 17,280 in³ = 74.81 US gallons (283.17 L) gross. Subtracting 10% for substrate and rock leaves 67.32 US gallons (254.85 L) of net water weighing 561.8 lb (254.9 kg). |
| Worked Case 2: Rimless 60 cm aquascape cube (60 x 45 x 42 cm fill height, 15% displacement) | Preloaded / test values | Rectangular Volume = L * W * H; US Gallons = Cubic Inches / 231; Liters = Cubic Centimeters / 1000; Net Volume = Gross Volume * (1 - Displacement% / 100) | Gross water volume is 113.40 L (29.96 US gal). With 15% soil and stone displacement, net water volume is 96.39 L (25.46 US gal), requiring a 24.10 L weekly 25% water change. |
How to use Aquarium Volume Calculator step by step
Use a tape measure on the inside of the glass (or subtract twice the glass thickness from outer measurements) before running the calculation.
Select unit and aquarium shape
Choose Inches or Centimeters and select Rectangular, Cylinder, or Bowfront geometry.
Enter interior length, width, and water height
Input the inside length, front-to-back width, and actual water column height from bottom glass to the waterline.
Set hardscape displacement and calculate
Enter a displacement percentage (typically 10% for planted gravel tanks or 20% for heavy reef rock) and click Calculate Tank Volume.
Worked examples for Aquarium Volume Calculator
Compare a standard 48-inch tank against a rimless cube to see net dosing volume.
Standard 75-gallon footprint (48 x 18 x 20 in water height, 10% displacement)
Interior water volume is 17,280 in³ = 74.81 US gallons (283.17 L) gross. Subtracting 10% for substrate and rock leaves 67.32 US gallons (254.85 L) of net water weighing 561.8 lb (254.9 kg).
Rimless 60 cm aquascape cube (60 x 45 x 42 cm fill height, 15% displacement)
Gross water volume is 113.40 L (29.96 US gal). With 15% soil and stone displacement, net water volume is 96.39 L (25.46 US gal), requiring a 24.10 L weekly 25% water change.
Measure to the waterline, not the top rim
Leaving 1 inch of air gap at the top of a 48 x 18 in tank reduces water volume by 3.74 US gallons (14.16 L) before any gravel is added.
How to interpret the Aquarium Volume Calculator output
Use Net Water Volume for chemical dosing and Gross + Hardscape weight for floor load checks.
The headline result shows Net Water Volume in US gallons and liters. Breakdown cards display Gross capacity, Water weight (freshwater at 8.345 lb/gal), 25% water change volume, and Top water surface area.
Input limits, assumptions, and related tools
Keep saltwater density and glass weight in mind when estimating structural load.
Water weight figures reflect only the net liquid water at 1.00 kg/L (8.345 lb/gal). Marine saltwater at 1.025 specific gravity weighs ~2.5% more, and the empty glass tank plus wet sand or rock typically adds 20% to 35% on top of the water weight.
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Open toolAquarium Volume Calculator: common questions
Answers about using Aquarium Volume Calculator and understanding its results.
Why is my calculated water volume smaller than the tank's advertised gallon rating?
Manufacturers label aquariums using exterior dimensions including glass thickness, plastic trim, and full rim height. Subtracting glass thickness, 1 inch of top headspace, and 10% substrate displacement typically leaves 80% to 85% of the nominal label volume.
How many cubic inches are in 1 US gallon of aquarium water?
One US liquid gallon equals exactly 231 cubic inches (3.785411784 liters). Dividing interior L * W * H in inches by 231 gives gross capacity in US gallons.
How much does aquarium water weigh per gallon and per liter?
Freshwater at room temperature weighs approximately 8.345 pounds per US gallon (1.00 kilogram per liter), not counting the weight of the glass tank itself, stand, gravel, or rock.
Should I dose aquarium medications using gross volume or net water volume?
Use net water volume (after subtracting substrate, rockwork, and headspace) so you do not overdose sensitive fish or invertebrates.
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