How To Find Soil Volume (3 Key Formulas To Know)

Need to fill up a container or raised bed with soil? You can find the volume if you have the right formula – and keep track of the units.

So, how do you find soil volume? To find soil volume, multiply the area of a container by its height. For a box, the volume is LxWxH (length x width x height). For a circle, the volume is πR²H (R = radius). For an ellipse (stretched circle), the volume is πABH (A is half the width of the narrowest part, B is half the length of the longest part).

Before you do your calculations, remember to measure all dimensions in the same units! For example, measure length, width, and height of a garden box in inches (or measure all in feet – just be consistent!)

In this article, we’ll talk about how to find soil volume for different shapes. We’ll go step-by-step on what you need to measure. If you already know your dimensions, you can use our trusty soil volume calculator instead (and get an email summary with your results!)

Try the soil volume calculator!

Let’s get started.

How To Find Soil Volume

To find the soil volume of a container, garden box, or raised bed, we multiply the area by the height:

V = AH (Volume = Area x Height)

pottings soil mix plant in container — To find the volume of a container for soil, multiply the area of the base by the height.

The trick is this: the area of the container will depend on its shape:

For a rectangle, the area is LxW (Length x Width)
For a square, the area is LxL (Length x Length, since Width = Length for a square)
For a circle, the area is πR² (Pi x Radius x Radius, where π is about 3.14)
For an ellipse, the area is πAB/4 (Pi x Width x Length/4, where π is about 3.14)

Note: when measuring your container, use the same units for each measurement. For example, if you measure the length as 10.5 feet, you should measure the width as 4 feet (not 48 inches). Basically, just be consistent with your units.

The pictures below will help you to figure out which dimensions to measure and record for your container.

Rectangle_Image — For a container with a rectangular base, you will need to measure both length and width to find area.

Square_Image — For a container with a square base, you will only need to measure width (since it is the same as the length).

Circle_Image — For a container with a circular base, you will only need to measure diameter (divide by 2 to get the radius).

Ellipse_Image — For a container with an elliptical base, you will need the length and width (at the widest and narrowest parts).

Ok, now you just need to plug those dimensions into the proper formula to find the area. Remember:

For a rectangle, the area is LxW (Length x Width)
For a square, the area is WxW (Width x Width, since Width = Length for a square)
For a circle, the area is πR² (Pi x Radius x Radius, where Pi is about 3.14)
For an ellipse, the area is πAB/4 (Pi x Width x Length/4, where Pi is about 3.14)

Ok, now you have the area of your shape. It’s time to find the height of the container.

Remember: measure in the same units that you used before. Also, only measure the height up to where you will fill the container.

For example, if your raised bed is 2 feet high, but you only want it ¾ full, then your height should be 1.5 feet (not 2 feet).

raised bed image homepage — Measure the height of your container up to where you will fill it.

Ok, now you’ve got the area and height. Just multiply them together to get the volume!

V = AH (Volume = Area x Height)

How To Find Soil Volume For Pots

Ok, so the shape of some plant pots is a little weird. Most of them are not shaped like a perfect cylinder. Instead, they look kinda like … part of a cone?

plant pot 1 — A plant pot kind of looks like a cylinder with the thinnest part chopped off.

Yes, a plant pot is shaped like part of a cone – it is like a big cone minus a smaller cone (like you started with a whole big cone and chopped off the top.)

plant pot (big cone minus small cone) — A plant pot looks kind of like a cone with the top cut off (or a big cone minus a little cone).

The volume of a cone is πR²H/3, where R is the radius of the base (a circle) and H is the height of the cone (and π, or Pi, is about 3.14).

The volume of a plant pot is the volume of the large cone minus the volume of the small cone, or:

V_pot = V_{large_cone} – V_{small_cone}

If we use R and H for the dimensions of the large cone, with r and h for the dimensions of the small cone, we get:

V_pot = πR²H/3 – πr²h/3
V_pot = π(R²H – r²h)/3

To find r, measure the diameter of the narrowest part of the pot and divide by 2.

To find R, measure the diameter of the widest part of the pot and divide by 2.

Now, put two straightedges flush with the side edges of the pot to “extend” the sides and see where they meet. The “extra” height (beyond the bottom of the pot) is h. (See the marked diagram below for help seeing this).

plant pot (big cone minus small cone) with dimensions marked full size — The value of h (height of the little cone) is how far beyond the bottom of the pot you would have to go to make the sides meet at a point (tip of the cone). H is the height of the full cone.

Finally, measure the height of the pot and add h to get H.

Then, plug in R, r, H, and h into the equation from before (repeated below) to find the volume.

V_pot = π(R²H – r²h)/3

How Much Is 1 Cubic Foot Of Soil?

1 cubic foot of soil is how much would fill up a cube with side length 1 foot (see below).

This cube is also 12 inches by 12 inches by 12 inches. So, its volume is 12³ = 1728 cubic inches.

Another way to think of it is this: a cubic foot holds about 7.5 liquid gallons. So, 1 cubic foot of soil would fill up one and a half 5-gallon buckets.

Of course, this depends on how much you pack the soil down. The weight depends on how wet the soil is.

How Much Is 1 Cubic Yard Of Soil?

1 cubic yard of soil is how much would fill up a cube with side length 1 yard (see below).

This cube is also 3 feet by 3 feet by 3 feet. So, its volume is 3³ = 27 cubic feet.

Another way to think of it is this: a cubic foot holds about 7.5 liquid gallons, and a cubic yard (27 cubic feet) holds 27 times as much, or about 202.5 gallons. So, a cubic yard of soil would fill up 40 and a half five-gallon buckets!

Once again, it depends how much you pack the soil down – and the weight depends on how wet the soil is.

How Much Soil Do I Need For A Raised Bed?

The amount of soil you need for your raised bed depends on the shape and dimensions. However, assuming a box (with a rectangular base), we can use the guidelines below (volumes listed in cubic feet).

Dimensions (feet)	1 ft	1.5 ft	2 ft	2.5 ft	3 ft
2×2	4	6	8	10	12
2×3	6	9	12	15	18
2×4	8	12	16	20	24
3×3	9	13.5	18	22.5	27
3×4	12	18	24	30	36
3×5	15	22.5	30	37.5	45
3×6	18	27	36	45	54
3×8	24	36	48	60	72
4×4	16	24	32	40	48
4×6	24	36	48	60	72
4×8	32	48	64	80	96

Conclusion

Now you know how to find soil volume for containers of all shapes and sizes. Just remember to keep track of units, and convert as needed (e.g. cubic feet to cubic yards).

Try the soil volume calculator!

Learn what you can use to fill up raised garden beds here!

I hope you found this article helpful. If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy!

~Jonathon

To find books, courses, seeds, gardening supplies, and more, check out The Shop at Greenupside!