The Triangular Planter Volume calculator computes the volume (V) of a triangular shaped planter based on the side lengths (a, b, c) and (h) height (see diagram). 
INSTRUCTIONS: Choose units and enter the following:
- (a) Length of side a
- (b) Length of side b
- (c) Length of side c
- (h) Height of planter or desired height of soil in the planter
Volume (V): The calculator returns the volume in cubic feet. However, this can be automatically converted into other volume units via the pull-down menu next to the answer. The calculator also returns the number of soil bags of the following sizes:
- 1 ft3
- 1.25 ft3
- 2.5 ft3
- 8 quarts
- 32 quarts
- 64 quarts
IMPORTANT NOTE: To compute the amount of soil needed in the planter, use the interior dimensions of the container, and use the top diameter associated with how high you want to fill the container. If you wish to fill to the brim, it is the full inner height.
The Math / Science
This calculates the volume of a triangular shaped planter. Enter the length of the three sides of the planter (a,b,c) and the (h) height of the interior of the container (see diagram), then this formula will provide the volume of the container. This answers the following questions:
- How much soil will my triangular planter hold?
- How much water will my triangular container hold?
- How much potting soil do I need?
If you do not intend to fill the container to the top, this formula will over estimate unless you use a depth (d) that matches your expected top surface inside the container. Unless it's a very large container, and/or you are only using a small portion of the container, the overage should be small.
The Garden Soil Price Survey information is as follows:
- Date: 6/11/21
- Store: Multiple Sources
- Garden Soil (1 ft3): $5.99
- Garden Soil (1.5 ft3): $6.49
- Garden Soil (2 ft3): $8.49
- Potting Mix (1.25 ft3): $8.74
- Potting Mix (2.5 ft3): $12.36
The Pricing Data can be used the the Raised Planter calculator.
The Math
This formula is based on the volume of a triangular column in 3-D geometry.