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Aquarium Volume Calculator

Calculate aquarium volume in liters and gallons from dimensions. Get fish stocking recommendations based on the 1 inch per gallon rule and tank shape.

90%

Account for gravel, rocks, decorations, and equipment. Typical: 85-90%

Liters
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usable: —
US Gallons
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usable: —
UK Gallons
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usable: —
Water Weight
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🐟 Fish Stocking Guide (based on usable volume)

Using the "1 inch of fish per gallon" rule. Actual capacity depends on species, filtration, and maintenance.

Small fish (1")
Neon tetra, guppy, endler
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Medium fish (3")
Molly, platy, dwarf gourami
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Large fish (6"+)
Angelfish, discus, oscar
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About This Tool

Planning a new aquarium or wondering how many fish your tank can hold? This calculator gives you everything you need — volume in liters and gallons, water weight, and fish stocking recommendations. Enter your tank's length, width, and height. The calculator handles rectangular tanks, bow-front tanks, and cylinder/column tanks. You'll see the total volume, usable water volume (accounting for gravel and decorations), and how many fish of different sizes your tank can comfortably support. Whether you're setting up a nano tank, a community aquarium, or a large display — start here to get your numbers right before buying fish.

How to Use

1. Select your tank shape (rectangular, bow-front, or cylinder) 2. Enter dimensions in your preferred unit (cm, inches, mm) 3. Adjust the "usable volume" percentage to account for gravel, rocks, and decorations (typically 85-90%) 4. View volume in liters and US/UK gallons 5. Check the fish stocking guide for your tank size 6. Click "Copy Link" to save your tank configuration

Formula

Rectangular: V = L × W × H Bow-front: V ≈ L × W × H × 1.1 (varies by bow depth) Cylinder: V = π × r² × H Fish stocking (general freshwater): 1 inch of fish per 1 US gallon (conservative) 1 inch of fish per 2 liters Small fish (1"): 1 per gallon Medium fish (3"): 1 per 3 gallons Large fish (6"+): 1 per 10+ gallons Water weight: 1 liter = 1 kg, 1 US gallon = 8.34 lb

Frequently Asked Questions

How do I calculate aquarium volume in liters?
Multiply length × width × height in centimeters, then divide by 1,000. For example, a 60×30×40 cm tank = 72,000 cm³ ÷ 1,000 = 72 liters. For inches, multiply L×W×H, then multiply by 0.01639 to get liters (or divide by 231 for US gallons).
How many fish can I put in my aquarium?
The classic rule is 1 inch of fish per 1 US gallon (or 1 inch per 2 liters). A 20-gallon tank can hold about 20 inches of fish — for example, 10 two-inch fish or 20 one-inch fish. This is a starting guideline; actual capacity depends on filtration, fish species, and maintenance routine.
How many gallons is a 60×30×40 cm tank?
60×30×40 cm = 72 liters = 19 US gallons = 15.8 UK gallons. This is a popular 'standard 20 gallon' size, suitable for a small community tank with 15-20 small fish or 6-8 medium fish.
How much does a full aquarium weigh?
Water weighs 1 kg per liter (8.34 lb per US gallon). A 100-liter tank holds 100 kg of water alone — add 10-15 kg for the tank, gravel, and decorations. A filled 100L tank weighs about 115-120 kg (250-265 lb). Always place aquariums on sturdy, level surfaces.
What is usable vs total volume?
Total volume is the tank's maximum capacity. Usable volume accounts for space taken by gravel (2-3 inches deep), rocks, plants, and equipment. Typically 85-90% of total volume is actual water. Use usable volume when calculating fish stocking.
How big should a beginner aquarium be?
20-30 gallons (75-115 liters) is ideal for beginners. Larger tanks are more stable (temperature, chemistry) and more forgiving of mistakes. A 10-gallon tank is harder to maintain than a 20-gallon. Avoid tanks under 10 gallons unless you're experienced.
How many neon tetras in a 10 gallon tank?
Neon tetras grow to about 1.5 inches. Using the 1 inch per gallon rule, a 10-gallon tank can hold 6-8 neons comfortably. They're schooling fish, so keep at least 6 together. Account for other fish and decorations when calculating total stocking.