How to calculate how much soil needed?

balaji27

Hello Team,

I would like to make a bed in the front yard with the sleepers but the shape of the yard makes it challenging for me to calculate the amount of soil required to fill. Would you please advise me the quantity of soil required or how to calculate it? Please refer to the front yard pic and the measurements for your review. I am planning to keep 200mm height, please let me know if you need any further information.

Thanks

Balaji.

EricL

Hello @balaji27 

Looking at your sketch, the bed is roughly a wedge shape in the corner, with 5600 mm across the top, 4500 mm down the side, 1850 mm along the bottom straight section, and then a curved side of about 6700 mm. A good way to handle a shape like this is to approximate the curved side as a straight line first, then allow a little adjustment.

If I join the top-right corner to the point where the curve meets the bottom (so it becomes a four-sided shape), that shape can be treated as a rectangle plus a right triangle. The rectangle is 1850 mm by 4500 mm, and the triangle is 3750 mm by 4500 mm. Converting to metres and adding those together gives an area of about 16.8 square metres. Because your actual side is curved and cuts into that corner a bit, the true area will be smaller. From the curve drawn and the photo, a realistic allowance is to take off roughly 10–20%, which brings the garden bed area down into the ballpark of about 14–15 square metres.

You are planning on 200 mm (0.2 m) of soil depth. Volume is area multiplied by depth, so 14–15 m² × 0.2 m gives around 2.8–3.0 cubic metres of soil. In practical terms I would work with 3 cubic metres of soil mix for this bed. That will comfortably cover the space to about 200 mm deep, with a little spare to allow for settling and to keep the finished level just under the top of the sleepers.

If you need further assistance, please let us know.

Eric