Tank Setup & Sizing Calculators

Plan the tank before you buy it

Almost every aquarium problem that is expensive to fix starts at planning: a tank too heavy for the stand or floor, a stand that is not level, glass too thin for the water height, or a budget that covers the tank but not the rest. The tools on this page work out volume, weight, load, substrate, glass and cost before you commit, and the dimension charts give you the footprint of the most common sizes.

Which calculator answers which question

• How many gallons? The Tank Volume Calculator gives gallons and liters from inside dimensions.
• How heavy when full? The Tank Weight Calculator adds water, glass, substrate and decor.
• Can the floor take it? The Stand Floor Load Calculator spreads the weight over the footprint.
• How much substrate? The Aquarium Substrate Calculator works in pounds and bags.
• How thick should the glass be? The Aquarium Glass Thickness Calculator gives a planning estimate.
• What will it cost? The Tank Setup Cost Planner gives a rough range.
• What are the dimensions? The Fish Tank Dimensions Calculator and the 20, 20 long, 40 breeder and 75 gallon pages list standard sizes.

Gallons, pounds and floors

A U.S. gallon is 231 cubic inches, so the volume of a rectangular tank is length times width times height in inches, divided by 231. Water weighs about 8.34 pounds per gallon, so a 55 gallon tank holds about 459 pounds of water before you add the glass, stand, substrate and decor, and the total can pass 600 pounds. That weight sits on the tank's footprint, so a long, narrow tank loads the floor differently from a square one. The floor load tool compares the load per square foot with a typical residential allowance, and for anything large, on an upper floor or in an older house, a structural check is wise.

Glass is a safety question

Glass thickness depends mainly on water height, because pressure rises with depth, and on the length of the unsupported panel. The tool uses common hobbyist bands and steps up for a long panel, which makes it conservative, but it is a planning estimate and not an engineering calculation. Buying a commercial tank means the maker has already done the engineering. For a do-it-yourself build, a large tank or an unusual shape, get a real calculation from a glass supplier or tank builder.

Substrate and cost

Substrate weight depends on volume and on the material, since sand packs more tightly than gravel and weighs more for the same depth. Plan for a depth that suits the plants and fish you keep. The cost planner gives a rough range per gallon for a basic freshwater, a planted or a reef setup, covering the tank, filter, heater, lighting, substrate and basic decor, but not livestock or ongoing supplies. Real costs vary widely with brand, new or used gear and how elaborate the scape is.

Common mistakes

• Forgetting the weight of everything but water. Glass, stand and rock add a lot.
• Assuming a stand is level and strong. Check it before filling.
• Going by the label gallons. A tank's real volume is lower once it holds substrate and headspace.
• Skipping the budget for equipment and livestock. The tank is only the start.