Bathroom and kitchen sinks come in all shapes and sizes. They can be round, oval or square in shape, big or small and shallow or deep. The way they attach to the counter also varies. Some are considered self-rimming, while others mount to the underside of the counter. To measure for a sink, take into account the dimensions side to side and front to back, as well as the depth.
Measure the size of the sink cabinet. This will determine the maximum width in which you can install. Open the cabinet under the current sink. Lay the tape measure from the inside of the face frame on the left side to the inside of the frame on the right side. If the cabinet is 34 inches wide and the face frame is 1 1/2 inches on each side, the sink should be 31 inches wide.
Run the measuring tape from the inside front of the sink to the inside at the rear of the sink. Subtract the size of the rim for an accurate reading. It's a good idea to write down the measurement of the rim, too, if you want a new sink with the exact same measurements.
Determine the height of the sink. This is the dimension from the top of the cabinet to the top of the cross rail of the sink base cabinet. Do not use the counter top in this measurement, but the top of the cabinet. The typical measurement is 9 to 10 inches.
Figure out how much space is available between the sink and the wall. Most new sinks need at least 15 inches of space from the center of the bowl to the nearest wall.
Write down all measurements and bring them with you when buying a new sink. Choose a sink with the same dimensions, or slightly larger if you are willing to cut a larger hole in the counter top.