How to use the Trapezoid Cubic Feet Calculator
- Identify the two parallel edges on the trapezoid end face. Measure the perpendicular gap between them and the extrusion length.
- Choose the shape mode, where available, and a unit for each dimension. Enter the number of identical objects.
- Select Calculate. Review the result and its working; if you change an input, calculate again before copying or sharing.
Trapezoid formula
Convert each length to feet, apply the displayed solid-volume formula, then multiply by the number of identical objects.
(a + b) × cross-section height × length ÷ 2
What the terms mean
- Parallel side a
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Parallel side b
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Perpendicular trapezoid height
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Prism length
- A measured length in the selected unit; it is converted to feet before volume is calculated.
- Number of identical items
- The whole-number count of objects with the same entered dimensions.
Trapezoid worked examples
Measure a trapezoidal prism
The parallel sides of a trapezoid are 2 ft and 4 ft, separated by 3 ft. The prism extends for 10 ft.
- (a + b) × perpendicular height × length ÷ 2
- a = 2 ft
- b = 4 ft
- trapezoidHeight = 3 ft
- length = 10 ft
- 90 ft³ × 1 = 90 ft³
Answer: 90 ft³. Cubic yards: 3.333333 yd³; Litres: 2,548.516193 L.
Measure a smaller trapezoidal section
Use parallel sides of 3 ft and 5 ft, a perpendicular separation of 2 ft and a prism length of 6 ft.
- (a + b) × perpendicular height × length ÷ 2
- a = 3 ft
- b = 5 ft
- trapezoidHeight = 2 ft
- length = 6 ft
- 48 ft³ × 1 = 48 ft³
Answer: 48 ft³. Cubic yards: 1.777778 yd³; Litres: 1,359.208636 L.
Trapezoid Cubic Feet Calculator FAQs
Do the parallel sides need the same length?
No. Their average sets the trapezoid area. Equal sides reduce this formula to a rectangular prism.
Does this handle any four-sided shape?
No. The end face must have a pair of parallel sides and a measurable perpendicular height.
Measurement guide for Trapezoid
Identify the parallel sides first. Their perpendicular separation is different from the length of either sloping side.
Assumptions and limits
A two-dimensional trapezoid has no volume until a prism length is specified. The cross-section must remain constant.
Check your result
Check the dimensions converted to feet in the working. For similar solids, doubling every dimension increases volume by a factor of eight.