Make the curtains
Decide where your curtain rod will go and how far below the window you want the curtains to hang. Measure this distance and add 32.5 cm (13 inches), which is 20 cm (8 inches) for tabs and 12.5 cm (5 inches) for a hem. This is your length.
Decide how far over the frame you want your curtains to extend on the sides. Measure from side to side and add 25 percent. For example, if you measure 50 cm (20 inches) add 12.5 cm (5 inches). This is your width.
Use these measurements to calculate how much fabric you'll need.
Get the fabric and preshrink it.
Cut out your curtains according to your measurements, one piece per window.
Measure and cut the tabs.
Narrow-hem both long sides.
Narrow-hem the tabs.
Machine hem the bottom of the curtains.
Bend the tabs over backward so that the fabric is wrong side in. Stitch by machine or hand.
Form the tabs
Visualize a castle. Tab-top curtains look just like the crenellations on a castle. Your goal is to create tabs that alternate with empty spaces of about equal width.
Measure the width of your curtain.
Calculate how wide you want your tabs to be and how many of them will fit. The exact measurements don't matter, but you'll need an odd number of tabs and spaces in total, because you need one more tab than you have spaces. Tabs and spaces should be 7.5 cm to 12.5 cm (3 to 5 inches) wide, and each curtain should have at least five tabs.
Cut out the spaces between the tabs.
At the cut corners, make a 1.3 cm (1/2 inch) diagonal cut, so that the tabs will lie smooth after hemming.
Turn over 6 mm (1/4 inch) and press to narrow-hem.
Turn over another 6 mm (1/4 inch) and press again.
Turn over half your hem allowance and press if you're using a standard machine hem.
Turn over the other half of your hem allowance and press again.