Fish Tank Weight Calculator
Calculate the total weight of your fish tank including water, glass, and substrate. Check if your floor can support your aquarium with our free weight calculator.
Weight Breakdown
Common Tank Weights
| Tank Size | Dimensions | Water (lbs) | Total (lbs) | Total (kg) |
|---|---|---|---|---|
| 5 Gallon | 16" × 8" × 10" | 42 | 123 | 55.8 |
| 10 Gallon | 20" × 10" × 12" | 83 | 208 | 94.3 |
| 20 Gallon Long | 30" × 12" × 12" | 167 | 365 | 165.6 |
| 29 Gallon | 30" × 12" × 18" | 242 | 486 | 220.4 |
| 40 Gallon Breeder | 36" × 18" × 16" | 334 | 683 | 309.8 |
| 55 Gallon | 48" × 13" × 20" | 459 | 866 | 392.8 |
| 75 Gallon | 48" × 18" × 20" | 626 | 1,122 | 508.9 |
How It Works
This calculator computes the total weight of your aquarium by summing three components: water weight, glass weight, and estimated substrate weight.
Water weight is calculated as gallons × 8.34 lbs/gallon (the weight of freshwater). Glass weight is estimated from the total surface area of all six panels using a standard density of 0.0907 lbs per square inch for ¼" glass. Substrate weight assumes a 2-inch deep gravel bed across the tank footprint.
Choose from common tank sizes with pre-set dimensions, or enter custom dimensions for non-standard tanks. Results are shown in both pounds and kilograms.
The floor support warning triggers at 500 lbs to remind you to check structural capacity, especially on upper floors or in older buildings.
Frequently Asked Questions
How much does a gallon of aquarium water weigh?
One gallon of freshwater weighs approximately 8.34 pounds (3.78 kg). Saltwater is slightly heavier at about 8.56 pounds per gallon due to dissolved salts. This means a 55-gallon tank holds roughly 459 pounds of water alone, before accounting for the tank, substrate, and decorations.
Can my floor support a large aquarium?
Most modern homes can support aquariums up to 55 gallons on the first floor without issues. For tanks over 75 gallons (which weigh 700+ pounds filled), place the tank perpendicular to floor joists to distribute weight across multiple joists. Upper floors, older homes, and mobile homes may need structural reinforcement. When in doubt, consult a structural engineer.
Do I need a special stand for a heavy aquarium?
Yes. Never place an aquarium on furniture not designed for the weight. A filled 20-gallon tank weighs about 225 pounds. Aquarium stands are engineered to distribute weight evenly and support the tank frame properly. Using an improper stand can cause uneven stress, leading to seal failure or cracked glass.
How does substrate affect total tank weight?
Substrate typically adds 1-2 pounds per gallon of tank capacity. A 2-inch deep gravel bed in a 20-gallon long tank adds roughly 20-25 pounds. Sand is slightly lighter per volume than gravel. Planted tank substrates like Fluval Stratum are significantly lighter. The weight calculator estimates substrate based on a standard 2-inch gravel depth.