Square Inches Calculator

What the square inches calculator does

For small, flat things, square inches is the unit that fits, where square feet would be an awkward fraction. This works it out. You give it a length and a width, and it returns the area in square inches, taking your measurements in whatever unit you have.

It is the area tool for the small scale. Below is how it works and where the unit earns its keep.

How to use it

1. Enter the length and width, each with its own unit. They need not match.
2. Press Calculate for the area in square inches, or Reset to clear it.

How the area is worked out

Area is length times width, once both are in inches:

Square inches = length × width

The calculator converts each measurement to inches first, whatever unit you entered it in, then multiplies the two. That is the whole of it for a rectangle, which covers most small flat pieces.

Square inches and square feet

The link between square inches and square feet surprises people, because it is not 12. A square foot is a square 12 inches on each side, so it holds 12 times 12, which is 144 square inches. That squaring is why areas grow so much faster than lengths when you change units.

So to go from square inches to square feet, divide by 144, and to go the other way, multiply. A 12 inch tile is exactly one square foot, 144 square inches, which is a handy figure to keep in mind when you are switching between the two.

A worked example: a small panel

Say you are measuring a panel 8 inches long and 10 inches wide.

The area is 8 × 10 = 80 square inches. Since 144 square inches make a square foot, that panel is a little over half a square foot.

So a piece that fits in your hand comes out as a tidy number in square inches, where in square feet it would be an unhelpful fraction.

Where square inches fits

Square inches suits anything small and flat. Craft and hobby materials, sheet metal and plastic offcuts, small panels, tiles, and labels are all sized comfortably in it, where feet would force you into decimals. It is also the unit for some engineering figures, like pressure, which is measured per square inch.

So when the thing you are measuring is the size of a book or smaller, square inches keeps the numbers sensible. For anything room-sized, the square footage calculator works in the larger unit.

Questions people ask

How do I calculate square inches?

Multiply length by width, with both in inches. An 8 by 10 inch panel is 80 square inches. The calculator converts other units for you.

How many square inches are in a square foot?

144, because a square foot is 12 inches on each side, and 12 times 12 is 144.

How do I convert square inches to square feet?

Divide by 144. So 288 square inches is 2 square feet.

Is a 12 inch tile one square foot?

Yes. A 12 by 12 inch tile is 144 square inches, which is exactly one square foot.

References

A quick note on the numbers. The area is plain geometry, length times width. The conversions to inches, and the fixed relationship that a square foot is 144 square inches, follow the US National Institute of Standards and Technology guide, where an inch is defined as exactly 25.4 millimeters.

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (SI). https://www.nist.gov/pml/special-publication-811