Carpentry Math

The square of the hypotenuse of a right triangle is equal to the sum of the squares of the other two sides.  The square of side A plus the square of side B equals the square of side C.

A² + B² = C²

The square of one side of a right triangle equals the square of the hypotenuse minus the square of the other side.  The length of the square of side A equals the square of side C minus the square of side B.

A² = C² - B²

The 3-4-5 rule of a right-triangle is the best way to square two walls.  If one side of a right-triangle is three feet and the other is four feet and the hypotenuse is five feet, then angle 'A' has got two be 90 degrees (see diagram at right).  If you want to square something larger, you can use proportions of this same formula, such as 6-8-10.

5² = 4² + 3² or 10² = 8² + 6²

How to calculate square feet

The area of a triangle is equal to one-half the product of the base and height.

A = .5 x (B x H)

How to calculate area of a rectangle

To calculate the area of a rectangle, simply multiply side 1 by side 2.

A = S₁ x S₂

How to calculate the area of a trapezoid

To calculate area of a trapezoid, multiply its height by one-half the sum of the parallel sides.

A = .5 x (L₁ x L₂) x H

Calculate area of a circle

To calculate area of a circle, multiply the circumference by one-half the radius

A = C x .5(R)

To calculate area of a circle, multiply the radius² by 3.1416 (pi).

A = 3.1416 x R²

How to calculate circumference

To calculate circumference of a circle, multiply the diameter by 3.1416 (pi).

C = 3.1416 x D

How to calculate volume of a cylinder

To calculate the volume of a cylinder, multiply the radius squared x 3.1416 (pi) x the height of the cylinder.

V = 3.1416 x R² x H