What is the difference between cooktop dimensions and cooktop cutout dimensions?
The appliance dimensions of a cooktop are not the same as the cutout dimensions needed to install it. The appliance dimensions, shown in the above image, are the length and width of the cooktop surface that sits above your countertop. The cutout dimensions are the length and width of the opening in the countertop needed for installation. Cutout dimensions are always smaller than the appliance dimensions because cooktop surfaces extend beyond the cutout below for a more seamless integration with your countertops.
It’s important to note that cutout dimensions can vary from model to model, even among cooktops with the same appliance dimensions. For example, a 30" cooktop model from one brand can have a cutout dimension that differs from another 30" cooktop model. Although this variation is usually no more than 1½", it’s enough to affect whether a new model will fit an existing cutout. That’s why it’s important to know both dimensions when shopping for a new cooktop, even when you’re replacing an old cooktop with the same surface dimensions.