Aquarium Volume Calculator

Calculate your aquarium volume in US gallons and liters. Accounts for effective volume with substrate and decorations.

Aquarium Volume Calculator image

Use a tank dimension diagram with length, width, height, gallons, and liters.

Key Takeaways

Length x width x height in inches divided by 231 gives raw US gallons. Effective volume is usually lower after substrate, decorations, and air space.
A 24 x 12 x 16 inch tank is about 20 gallons before displacement. Planning around 85-90% effective water volume is usually safer.
Use calculator results as planning estimates and verify against equipment labels or species-specific care needs.

Aquarium Volume Calculator

Length (inches)

Width (inches)

Height (inches)

Effective volume accounts for substrate, decorations, and unfilled space (85% of raw volume).

Length x width x height in inches divided by 231 gives raw US gallons. Effective volume is usually lower after substrate, decorations, and air space.

A 24 x 12 x 16 inch tank is about 20 gallons before displacement. Planning around 85-90% effective water volume is usually safer.

Using outside tank dimensions when inside dimensions are meaningfully smaller.
Forgetting that substrate, hardscape, and an unfilled rim reduce actual water volume.
Using raw volume for medication dosing without checking the product label.

Multiply length × width × height in inches, then divide by 231 to get US gallons.

Effective volume is about 85% of the raw volume, accounting for substrate, decorations, and unfilled space.

Calculator formulas are simplified planning estimates for freshwater aquariums.
Equipment choices should be checked against manufacturer ratings and real tank conditions.
Stocking and health decisions should be adjusted for adult fish size, behavior, filtration, and water test results.

Find the right wattage heater for your aquarium based on tank size and temperature difference.

Check how many fish your aquarium can safely hold based on tank size and filter quality.

Calculate how much water to change and estimate nitrate reduction from water changes.

Estimate the total weight of your filled aquarium including water, substrate, and equipment.

Use your tank size and preferred fish to plan equipment and stocking.

Check whether two species can live together before stocking.