Reference data
Area and volume conversions
Square feet to square yards, metres and acres; cubic feet to cubic yards and metres — with the definition each one follows from.
Written and edited by Pablo Ruiz Quintero
Last reviewed 2026-09-16
How many square feet are in a square yard, a square metre and an acre?
Nine, 10.764 and 43,560 respectively. The one that catches people is the first: a yard is three feet, so three feels right — but area scales with the square of length, so a square yard is nine square feet. The same logic makes a cubic yard twenty-seven cubic feet, not three.
Area
| Unit | Square feet | Square metres | Where it comes from |
|---|---|---|---|
| 1 square foot | 1 | 0.0929 | The base unit for US building materials. |
| 1 square yard | 9 | 0.8361 | Three feet squared. Carpet is still quoted this way. |
| 1 square metre | 10.7639 | 1 | Follows from the inch being 25.4 mm exactly. |
| 1 acre | 43,560 | 4,046.8564 | One chain by one furlong — 66 ft × 660 ft. |
| 1 square inch | 0.006944 | 0.0006 | 144 to the square foot. |
| 1 hectare | 107,639.1042 | 10,000 | 10,000 m², or 2.471 acres. |
Volume
| Unit | Cubic feet | Cubic yards | Where it comes from |
|---|---|---|---|
| 1 cubic foot | 1 | 0.03704 | 7.48 US gallons of water. |
| 1 cubic yard | 27 | 1 | Three feet cubed. How bulk material is ordered. |
| 1 cubic metre | 35.3147 | 1.30795 | Metric equivalent, sometimes called a cube. |
| 1 cubic inch | 0.000579 | 0.00002 | 1,728 to the cubic foot. |
| 1 board foot | 0.083333 | 0.00309 | 144 cubic inches: 12 × 12 × 1 in of lumber. |
Length
| Unit | Feet | Metres | Where it comes from |
|---|---|---|---|
| 1 foot | 1 | 0.3048 | 0.3048 metres exactly, by definition. |
| 1 yard | 3 | 0.9144 | 0.9144 metres exactly. |
| 1 metre | 3.28084 | 1 | The definition everything else derives from. |
| 1 inch | 0.083333 | 0.0254 | 25.4 millimetres exactly, since the 1959 agreement. |
Why these numbers never change
Every figure on this page follows from a single definition: since the international agreement of 1959, the inch is exactly 25.4 millimetres. Not approximately — exactly. The foot, the yard, the mile and the square metre equivalence are all arithmetic from there.
That makes this the only table on the site with nothing to re-verify. A delivered price moves with the market and a bag yield changes when a manufacturer reformulates a mix; a conversion factor is fixed by agreement and stays fixed. The review date here records when the page was last read, not when the numbers last moved.
The two that are not what they look like
The acre is 43,560 square feet, which looks arbitrary because it is historical: one chain by one furlong, 66 feet by 660. It predates any attempt to make units round.
The board foot is in the volume table, not the area table, and that is the point. It is 144 cubic inches — a piece one foot square and one inch thick — so a twelve-foot board is twelve linear feet and some quite different number of board feet. Mixing the two is the most common ordering error at a lumber yard.
Using them
The square footage calculator applies all of these at once: measure in feet or metres, and it returns the area in square feet, square yards, square metres and acres, the perimeter in linear feet, and — if you give it a depth — the volume in cubic feet, cubic yards and cubic metres.
Send this to whoever is paying
The link carries your measurements, so whoever opens it sees the same numbers you are looking at — and you can come back to it yourself tomorrow with the delivery note in front of you.
Plain links, no tracking scripts. Nothing here reports back that you shared it.
About the author
Pablo Ruiz Quintero — Editor
Editor of MaterialsEstimator. Decides which documents count as a source, what every default value is, and where the line sits between what the reader parses and what the engines compute.
More about how this site is edited