Whether you are remodeling your kitchen or just replacing the kitchen sink, it is important to measure before ordering the sink. This is especially true when you plan to install an undermount sink. An undermount sink sits below the surface of the countertop, rather than on top of it like drop-in sinks do. Unlike drop-in sinks, undermount sinks need fairly precise measurements, because they will not cover the edges of the sink hole from the top.
Draw a rough sketch of your current sink on a piece of paper with a pencil. It does not have to be precise, just a representation of your sink to transfer the measurements you take.
Go under the sink cabinet. Measure the width of the existing sink hole at the back of the sink, from one side to the other. Write this measurement down. Measure the width of the front of the sink the same way and write down the measurement.
Take measurements for the depth of the sink on each side. Measure the hole from front to back with the tape measure. Write down the measurements on the corresponding sides of your drawing.
Measure from the back of the sink hole to the back of the sink cabinet.
Measure from the bottom of the counter to the bottom of the deepest bowl of the sink to determine the sink's depth. Record the measurement on your sketch.
Go to the top of the sink. Measure from the front of the counter to the backsplash. Make notations on your sketch for the location of the faucets.