Triangular Prism Volume Calculator
Calculate the volume of a triangular prism from its triangular base dimensions and prism length. Formula: V = (1/2) x b x h_t x l. Fast and reliable.
How to use this tool
- Enter triangle base, triangle height and prism length in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your volume and the full breakdown beneath it.
Formula
V = (1/2) x b x h_triangle x l
How it works
The cross-section is a triangle (area = ½bh), so V = ½ × b × ht × l.
Worked example
Prism b=5, triangle h=4, length=10
- Triangle area = (1/2) x 5 x 4 = 10
- V = 10 x 10 = 100
Volume = 100 cubic units
Common mistakes to avoid
- Mixing up the height of the triangular cross-section (h_triangle, perpendicular to the base of the triangle) with the length of the prism — these are two separate dimensions.
- Using a non-perpendicular measurement for h_triangle when the triangle is scalene or obtuse, resulting in an overestimate of the cross-sectional area.
- Forgetting the 1/2 factor for the triangular area and computing b * h_triangle * l instead of (1/2) * b * h_triangle * l.
Key terms
- What is the difference between base and length?
- The base is a side of the triangular face; the length is how far the prism extends perpendicular to that face.
- What is a prism?
- A prism is a 3D shape with two identical parallel polygonal ends connected by rectangular faces.
Frequently asked questions
- What is the difference between h_triangle and the prism length l?
- h_triangle is the altitude of the triangular face — the perpendicular distance from the base edge of the triangle to the opposite vertex. l is the length of the prism, meaning how long the shape extends in the third dimension. Both are needed for the volume.
- Can I use Heron's formula if I only know the three sides of the triangle?
- Yes. Compute the triangular area A_t using Heron's formula (s = (a+b+c)/2, A_t = sqrt(s(s-a)(s-b)(s-c))), then multiply by the prism length: V = A_t * l.
- What units does the result come out in?
- Volume is in cubic units. If all three inputs (b, h_triangle, l) are in metres, the volume is in cubic metres (m^3). Mixing unit systems will give wrong results.