A common question is,"How much stone do impregnating sealers cover?". Well, it depends on the sealer and the porosity of the stone. The porosity or absorbency of the granite, or marble, or travertine that you are sealing is a major factor. If the stone is very porous, then it will need 2, or sometimes 3 coats requiring a greater volume of sealer.
Also, sealers will vary and some sealers will cover a greater number of square feet of stone per ounce than others.
The SenGuard Permanent Marble & Granite Sealer will cover 50-200 sq. ft. depending on porosity. This sealer is the most advanced and will cover the greatest area per ounce. It contains 12 ounces and will cover up to 3x more stone per ounce of sealer than all other sealing products. Also, it is a permanent sealer, so you won't have to re-apply in the future.
A standard sealer like the Stone Care: Impregnating Marble & Granite Sealer (32 ounces) will cover 75 - 125 sq. ft. depending on porosity of the stone. This sealer is very good, but not permanent and will need re-application at some point in the future. Note that it covers less than SenGuard with nearly 3x the volume.
The important number to know is the number of square feet a sealer will cover and not the volume of the sealer purchased.
What it boils down to is that you can only make an estimate on the volume of a sealer needed (based on coverage numbers for that sealer) to effectively seal your specific surface. You simply have to apply the sealer (one, two or three coats...) until the surface is effectively sealed.
It is helpful to note that the average kitchen countertop is 40 - 50 square feet. So, for example, one bottle of SenGuard is almost always sufficient for one countertop. Usually, you'll have some left over to seal a small second countertop, etc.