Common size for Granite Marble (Natural Stone) slab is 55” X 96”. Very often some slabs can vary ten or more inches. Some times one, two inches would be all you need for your project, without purchasing an extra stone slab.
Natural Stone Slab Cut Layout and Planning.
Average Granite and Marble (natural stone) slabs are 55” X 96”. Some soapstone and limestone slabs are tend to be smaller about 63" x 79".
One think to keep in mind when choosing natural stone and picking out your perfect stone slab is, how the pieces will be layout (cutout). You may come across undesirable surprises, when choosing very “flowing”, “veiny” stone slab.
The economical way to layout (cutout) the Natural Stone slab.
Stone slab planned layout
click on the image for larger preview.
Seam preview after counter install
click on the image for larger preview.
Wouldn't it be nice, if we couldn't even notice the seams on our counter tops! Well it depends, what priorities we have, (to get most out of your stone slab, or to get most appealing final look). If you want to get more out of stone slab (more usable material), you probably end up with more seams on your countertops. And it will be hard to keep stone natural flow. Keep in mind seams are hard to hide and you will probably feel them every time when cleaning your counters.
Most likely you won’t have this problem, when you will go with consistent stone which has very little movement.
Take a look at the illustration on the left. Cutting stone this way, would be more efficient, you get less stone remnants. But in the final result the seam will be more visible, and the stone flow won’t feel right. Click on images for larger preview.
Planning for appealing, stone flow final result.
Stone slab planned layout
click on the image for larger preview.

Seam preview after counter install
click on the image for larger preview.
Same countertop layout, but this time we will plane ahead, how the countertop will look after stone is installed. Seam is less noticeable because we cut it in the stone area were material is about the same flow and color.
I personally prefer this layout, it feels right, and I know I will be looking at these countertops, for many years to come.
Note. These illustrations are here, just to demonstrate what can happened, when choosing flowing, veiny stone slab. Of course most stone fabricators are very well aware of how to plan stone slab layout, for most economical and spieling look.