How to Measure Measuring the surface area you are going to treat is the first step to determine how much material you need to order. Just take a tape measure and find out the length and width in feet and then multiply to find the number of square feet. Remember to measure all surfaces that you need to treat. For example troughs or drain paths have vertical areas that are in addition to the flat floor area. Similarly, concrete block run dividers have front and top edges, which could total an extra 5-10 square feet if they are 6" wide. The application rates for Deep Seal and Top Seal are at a rate of 150 square feet per gallon. So divide the total square feet by 150 and you will find out how many gallons you will need. The 150 square feet per gallon figure is an average figure, for average concrete with a light broom finish. Very smooth, power troweled finishes have a very tight surface, so they can absorb less material. You may get a coverage rate of 175 square feet per gallon, or up to 200 even. It is best to not order more than you need, even though the shelf life is very long. But it is worse to order too little and not be able to finish the job in the event it takes more than you anticipated. Since every slab of concrete it is different, it is pretty hard to tell just by looking. So safest bet...figure 150 square feet per gallon. The application rates of 150 square feet per gallon works out to only .85 ounce per square foot... really not much material... less than a shot glass of liquid spread over a square foot. The worst thing you can do, in my opinion is order too little material, then try to make it stretch out to finish the job. If you use too little material there is a risk that it will not work as it should (only makes sense, eh?). If you use too little Top Seal, you likely will have to add more after a year or two. But if you put the materials on at the specified rate, then you can expect five years or more until you would need to consider applying more material. On porous blocks, the application rate will be more material...so figure maybe 125 square feet per gallon... because of the more open surface. Once you find the number of gallons of Deep Seal and Top Seal you will need, just click here to find out prices. You'll notice that you can order "kits", equal amounts of Deep Seal and Top Seal, or at the bottom of the page you can order single gallons or five gallon buckets of either or both material in the event you need different amounts of each. Zeke wonders if you're as confused about measuring as he is!