When measuring square footage, a person is essentially measuring area, so they must determine what the shape of the area is. Calculate the area of an irregular surface area to determine square footage with tips from a math teacher in this free video on math lessons.

## Video transcription

Hi I'm Steve Jones and I'm going to tell you how to measure square footage. First of all square footage implies a measurement in feet but this applies in fact to a measurement in any unit you care to measure, it could be inches, it could be feet, it could be yards, it could be kilometers, it could be centimeters, it doesn't matter what unit you are working in but measuring square footage is measuring area and measuring area can be done either by calculating if you've got a regular area such as a square or rectangle length times width or using pie r squared so that is a formula telling you the area of those, or you can combine those for example a sports field has two semicircular ends and a rectangular center. So you've got the rectangle, length times width and you've got the area of the circle or half pie r squared for each end if it's a semicircle at each end. The real problem comes when you get an irregular surface, an irregular area. For example people often try and work out the area of their foot on the ground and that is an irregular area. You can't calculate. There is no formula for this and then what we do is we put it on to a grid and on the grid we measure the numbers of squares. This is one square so here we've got one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen squares. So we have got sixteen full squares but we have got a lot of half squares or not quite squares but for example we can estimate these and we can say well this square with that one and that one make up a square and another one and this one and that one are a half each add another one and this one and that one make another square and this one and this one make another square. Actually I should have marked that one. So actually we've got seventeen squares to be correct initially and then we've got these bits here. That one goes with that. That one and this one say another square and this one and this one another square and one more there and one more there so two more squares. So seventeen, eighteen, nineteen, twenty, twenty one, twenty two, twenty three, twenty four, twenty five square whatevers. If these were centimeter squares it would be square centimeters. If they were inch squares it would be square inches. This is a very accurate way actually of calculating the area of an irregular figure so if you want to measure square footage remember there are several ways of doing it One way is to calculate if it is regular. The second is if it is a combination of regular figures to calculate that. But if that all fails use a grid system and count up the number of squares and estimate for part squares and that will give you a simple way to find the area of an irregular figure.