Water & Liquid Tank Volume Calculator
Calculate the total and currently-filled volume of a liquid storage tank in liters, US/UK gallons, cubic meters, cubic feet and fluid ounces, plus the liquid's weight. Supports rectangular, vertical/horizontal cylinder, cone-frustum and capsule tanks.
Input
Tank Shape & Units
Dimensions
Fill & Liquid
Volume at this fill level, measured from the bottom up (horizontal cylinders use the circular-segment area; the capsule is approximated linearly).
Used to estimate the weight of the filled liquid.
Output
| Property | Value |
|---|---|
| No data yet | |
Guides
Work out how much liquid a tank holds — and how much is in it right now — for five common tank shapes. Enter the dimensions, pick a fill level, and the calculator returns the total capacity and the currently-filled volume in liters, US and UK gallons, cubic meters, cubic feet and US fluid ounces, plus an estimate of the liquid's weight. Everything runs in your browser; nothing is uploaded.
How to use it
- Pick a tank shape. Rectangular/box, vertical cylinder, horizontal cylinder, cone frustum (a tapered tank), or capsule (a cylinder with hemispherical ends).
- Choose your length unit — meters, centimeters, millimeters, inches or feet. Every dimension you type uses this unit.
- Enter the dimensions shown for that shape. A rectangular tank needs length, width and height; a cylinder needs diameter plus height or length; a frustum needs top and bottom diameters and height.
- Set the fill level from 0–100%. The filled volume is measured from the bottom up.
- Choose the liquid so the weight estimate uses the right density.
The formulas
Each shape uses its exact geometric volume, computed in meters internally:
- Rectangular: length × width × height.
- Vertical cylinder: π × r² × height.
- Horizontal cylinder: π × r² × length for the total. The filled volume is the harder case — a horizontal cylinder fills as a circular segment, so the tool computes the segment cross-sectional area
r²·θ − (r−h)·√(2rh − h²)(whereθ = acos((r−h)/r)andhis the liquid depth) and multiplies by the length. A half-full horizontal cylinder is exactly half its capacity, but at 25% depth it holds noticeably less than 25% of the volume — which is exactly why the segment formula matters. - Cone frustum: (π·h / 3) × (r₁² + r₁r₂ + r₂²), with the fill line's radius interpolated between the two ends.
- Capsule: a cylinder body plus a full sphere from the two hemispherical caps.
Unit conversions
Volumes are derived from cubic meters: 1 m³ = 1000 L, 1 US gallon = 3.785411784 L, 1 UK (imperial) gallon = 4.54609 L, 1 ft³ ≈ 35.3147 L, and 1 L ≈ 33.814 US fl oz. Weight is filled-liters × liquid density (water = 1.000 kg/L), then converted to pounds at 2.20462 lb/kg.
Which fill levels are exact?
Fill level is precise for rectangular tanks, vertical cylinders and horizontal cylinders. For the cone frustum it interpolates the radius at the liquid surface, and for the capsule the partial fill is a simple linear approximation rather than the true spherical-cap math — treat those two as close estimates below 100%.
Why does the filled volume differ from total × fill %?
Only for the horizontal cylinder. Because a round tank on its side fills as a segment, the relationship between depth and volume is not linear — a tank filled to 25% of its diameter holds less than a quarter of its capacity near the bottom and more near the middle.