Tank Volume Calculator
Estimate total capacity, filled volume, empty space, and fill percentage for ten common tank geometries.
Tank inputs
Live results
Capacity breakdown
Filled versus empty capacity
Volume detail
| Measure | Volume | Share of capacity |
|---|---|---|
| Total capacity | 1,696.46 L | 100.00% |
| Filled | 1,272.35 L | 75.00% |
| Empty | 424.12 L | 25.00% |
How to use this tank volume calculator
What this calculator does. It estimates a tank's ideal internal capacity, the volume currently filled, the remaining headspace, and the percentage full. It supports vertical and horizontal cylinders, rectangular prisms, vertical and horizontal capsules, vertical and horizontal oval tanks, cone-bottom and cone-top tanks, and standalone frustums. The result is a geometry estimate, not a certified calibration table or a structural design rating.
When to use it. Use it to check water-storage capacity, estimate how much liquid remains in a process vessel, compare candidate tank sizes, or plan transport and refill quantities. For regulated storage, custody transfer, hazardous materials, or pressure vessels, confirm dimensions and allowable working capacity with the manufacturer or a qualified engineer.
How to calculate. The calculator opens with a complete demonstration: a vertical cylindrical tank with a 1.2 m diameter, 1.5 m height, and 1.125 m fill depth. The example can be exported immediately. To calculate your tank:
- Select Tank shape.
- Choose the Dimension unit; changing it converts existing dimension values.
- Enter every visible required dimension. Use inside dimensions, not outside dimensions.
- Enter Filled height from the physical bottom of the tank. It cannot exceed the shape's maximum fill height.
- Select the Volume unit and read the live results, chart, and detail table.
- Choose Download Excel to save the current inputs and calculated outputs as an XLSX workbook. Reset clears the demonstration and all data; export remains unavailable until a complete valid set is entered again.
Input guide. Tank shape is required and determines which dimensions appear. Dimension unit accepts meters, centimeters, feet, or inches. Diameter is the inside circular diameter; for example, 1.2 m. Length is the axial tank length or the straight cylindrical section of a capsule. Height is the vertical inside height of rectangular, oval, or cylindrical forms. Width is required for rectangular and oval tanks. Bottom diameter and Cone height define a frustum or the tapered section of a cone-top/bottom vessel. Filled height is required, must be zero or greater, and must not exceed the maximum physical height. Plain decimal notation is accepted; comma decimals, scientific notation, units typed into the field, negative dimensions, and nonnumeric text are rejected. Volume unit changes only the displayed and exported unit, not the physical model.
Output guide. Total tank volume is the ideal geometric capacity. Filled volume is the volume below the entered liquid level. Empty volume is total minus filled and represents theoretical headspace. Fill percentage is filled volume divided by total capacity. Maximum fill height is the vertical extent used to validate the liquid depth. The Capacity breakdown, donut chart, and Volume detail table all use the same current model; zero filled height produces 0% full and full height produces 100% full.
Worked example. For the startup vertical cylinder, radius is 1.2 ÷ 2 = 0.6 m. Total capacity is π × 0.6² × 1.5 = 1.69646 m³, or 1,696.46 L. At a fill height of 1.125 m, filled volume is π × 0.6² × 1.125 = 1,272.35 L. The remaining headspace is 424.12 L, and the tank is 75.00% full.
Learn more. The NIST guide to SI volume units explains why the cubic meter is the SI volume unit and how liters relate to cubic decimeters. For the underlying geometry, see the solid-volume formulas for cylinders, cones, and frustums and the circular-segment method for partially filled horizontal cylinders.
Formula and interpretation notes
All calculations use consistent internal SI units. Linear dimensions are converted to meters, geometry is evaluated in cubic meters, and the result is converted to liters, US gallons, cubic feet, or cubic meters. For a vertical cylinder, the formula is:
Horizontal cylinders and horizontal capsules use circular-segment geometry because liquid depth does not increase volume linearly. Oval tanks use an ellipse-segment relationship. Frustums and cone-bottom/top tanks use similar-triangle scaling to determine the radius at the current liquid level. These distinctions matter: a tank that is half full by height is not always half full by volume.
Use internal measurements whenever possible. Exterior dimensions can overstate usable capacity because they include wall thickness. Real tanks may also have rounded corners, domed heads, baffles, fittings, slopes, dead zones, or required freeboard. Treat the result as a planning estimate and compare it with the manufacturer's capacity chart for operational decisions.