We used a method we called guestimate. Look around the the roof and guess how many squares. Write this number down and compare it to your total squares after you have added them up. This takes some experience and is not intended to be real accurate. It can give you a clue as to if your squares are in the ball park. e.g. If you wrote down 50 squares and adding your numbers totaled 25 then you need to investigate. The first and easiest thing to check is your written numbers, did you skip a written measurement ? Did you push a wrong button on your calculator ? The RoofCalculator program Number Details report contains the perfect check for this.

 Look around the roof and visually plan your sequence of measurements. Plan where you are going to start and finish. Don't jump all over the roof measuring here and there. Pre- label your estimate sheet having columns for Hips, Valleys, Eaves, Rakes and Ridge.  Measure everything in sequence, such as all the hips, then all the valleys, etc.

   Do not pad your measurements, such as 15' 1" = 16' etc. It's always better to know exactly where you are at. You can always add to your total squares, but know what your total squares are. The  one exception to this is your valleys, if you are using valley metal. You will have to add for  your laps, where your sheets lap one another and your lap at the top.

Pay attention when reading your tape measure and writing your numbers. Numbers can get transposed. There is a lot of difference between 34 and 43. When using a 100ft tape measure a lot of the time you are reading the tape measure upside down. e.g. roof is 60ft long x 34 = 2040 sq ft. , 60 x 43 = 2580 a lot of difference. 2580-2040 = 540 sq feet or 5.4 squares.