How to use the Tank / Vessel Cubic Feet Calculator
- Measure liquid depth vertically from the lowest inside point. For a horizontal cylinder, measure tank diameter and axial length.
- Select the tank shape and orientation. Enter internal dimensions and liquid depth from the bottom.
- Select Calculate. Review the result and its working; if you change an input, calculate again before copying or sharing.
Tank / Vessel formula
The selected geometry gives full capacity. Liquid depth determines the filled portion; a horizontal cylinder uses circular-segment area.
Box: L × W × fill; vertical cylinder: πr² × fill; horizontal: [r² acos((r − h)/r) − (r − h)√(2rh − h²)] × length
What the terms mean
- Tank length / cylinder height
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Tank width
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Tank height
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Cylinder diameter
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Liquid depth from bottom
- A measured length in the selected unit; it is converted to feet before volume is calculated.
Tank / Vessel worked examples
Find liquid volume in a half-full rectangular tank
A rectangular tank is 4 ft long, 3 ft wide and 2 ft high internally. Liquid is 1 ft deep from the bottom.
- Length × width × liquid depth
Answer: 12 ft³. Full tank capacity: 24 ft³; Fill percentage: 50 %; US gallons: 89.766234 US gal; Cubic yards: 0.444444 yd³; Litres: 339.802159 L.
Find liquid volume in a horizontal cylinder
A flat-ended horizontal cylinder is 4 ft long and 2 ft in diameter internally. Liquid depth is 1 ft, measured from the lowest point.
- Horizontal cylinder: circular segment area × length
Answer: 6.283185 ft³. Full tank capacity: 12.566371 ft³; Fill percentage: 50 %; US gallons: 47.00149 US gal; Cubic yards: 0.232711 yd³; Litres: 177.919994 L.
Tank / Vessel Cubic Feet Calculator FAQs
Can it measure a half-full horizontal tank?
Yes. Liquid depth equal to the radius gives half of the full circular-cylinder capacity.
Is cylinder length the liquid height?
For vertical mode it is total tank height; liquid depth is entered separately. For horizontal mode it is the cylinder’s axial length.
Measurement guide for Tank / Vessel
Measure liquid depth vertically from the lowest internal point. Select the correct cylinder orientation; the horizontal mode assumes flat ends.
Assumptions and limits
Models assume flat ends and a level tank. Domed ends, tilt and internal hardware change volume and need another model.
Flat-ended interior dimensions, level tank and no internal obstructions. Domed ends require a different model.
Check your result
Liquid volume should lie between zero and full capacity. A horizontal cylinder is half full when liquid depth equals its radius.