To calculate the subtotal amount and sales taxes from a total: 1  Ensure that the Find Subtotal (before tax) tab is selected.  2 Province of Sale - Select the province where the product buyer is located.3  For provinces that split GST from PST (such as Manitoba, Quebec and Saskatchewan) a No PST checkbox will appear.he second tab lets you calculate the taxes from a grand total including tax, and gives you the subtotal before tax. Useful for figuring out sales taxes if you sell products with tax included - or if you want to extract tax amounts from grand totals. 1  Calculator Instructions.
Measuring accurately, and rounding up slightly are the keys to figuring out the square footage of wallpaper needed. This method will give you plenty of wallpaper for matching up patterns, covering unusually shaped areas, and even repairing small mistakes without wasting money and leaving you with excess paper.
3. Measure an irregularly shaped room manually. If the room you are measuring is not a square or rectangular, you will need to measure each individual side of the roomâs perimeter. Work your way around the roomâs perimeter with a measuring tape, recording the length of each side of the room.easure the width and height of the wall. To calculate the area of a wall, use the standard (Width) x (Height) = Area formula. Using a measuring tape, measure the width and height of the wall.