Aquarium Volume Calculator

Exact volume in liters, US gallons, ft³ / m³ and water weight. Supports 7 shapes, headspace, substrate/decor displacement, presets, solve-for-dimension, fish stocking estimator, and a typical sizes table.

Basics

Unit System Gallons Type Water weight adjusts automatically Tank Shape Headspace (distance below rim)

Typical: 0.5–1.0″ (1–2.5 cm) Or Headspace by %

Leave blank to use distance above Number of Tanks We’ll multiply the net water volume

Common Size Presets (internal dimensions)

Quick Select

Preset tip

Presets fill inputs below. Adjust headspace & displacement to reflect your actual setup.

Dimensions

Length

Width

Height (internal)

Water Displacement (Substrate & Decor)

Substrate Depth

Average depth across footprint Substrate Coverage

Substrate Type (void %) Only solids displace water Solid Decor / Rock Volume

Solve for a Dimension (optional)

Target Net Volume

Uses current shape + headspace + displacement Solve Which? Provide the other dimensions

One-click

Water Volume & Weight

Enter your dimensions to see gross and net (after displacement) water volume in liters and gallons.

Gross Internal Volume

—

L • US gal • ft³ / m³

Displacement (Substrate + Decor)

—

L • US gal

Net Fill Volume (per tank)

—

L • US gal • cm³ / in³

Total Water (all tanks)

—

L • US gal

Water Weight (per tank)

—

kg • lb

Water Weight (all tanks)

—

kg • lb

Fish Stocking Estimator (Rule-of-Thumb)

Basis Heuristic only — species behavior and filtration matter. Avg Adult Size

Filtration/Experience Factor

Estimate

Calculate volume first; then we’ll estimate a safe starting count.

This guide is for peaceful community freshwater setups. Reduce stocking for large, messy, territorial, or sensitive species. Always research species adult size and bioload.

Typical Aquarium Sizes (Internal Dimensions)

Label	Dimensions (L × W × H)	Approx. Volume	Water Weight

Volumes assume internal dimensions and no displacement. Filled weight shown is water-only (glass, stand, rocks, substrate add extra). Use the calculator above for your exact setup.

Why Tank Volume Accuracy Matters

Stocking: match fish count to actual water volume, not nominal size.
Dosing: conditioners, fertilizers, and medications are per-volume.
Placement & safety: know total water weight before you pick a stand or location.

Formulas Used

Rectangular: A = L × W; V = A × H_water
Cube: V = edge³; H_water = edge − headspace
Cylinder: A = π (D/2)²; V = A × H_water
Half / Quarter Cylinder: V = (½ or ¼) × cylinder volume
Hexagon (regular): A = (√3/2) × F² (F = flat-to-flat); V = A × H_water
Bowfront: A = L × W_flat + circular segment(L, sagitta); V = A × H_water

Displacement subtracts solid volume only: footprint × substrate depth × coverage × (1 − void fraction) + solid decor liters.

Good Practice

Measure internal glass dimensions.
Account for headspace (distance or %).
Include substrate/decor displacement for net water volume.