First, follow the orange lines to measure the window width and height.
Next, as a rule of thumb, add a minimum 0.15m(15cm) allowance to each side of the measurement. This will allow the blind to overlap the window and reduce light leakage from the sides.
Note: The 15cm(6 inches) allowance is a general guide, it can be more depending on individual’s preference. The more overlap you have, the lesser will be the light leakage.
P.S. In the above example, there is a beam right above the window. As the blind’s headrail will be mounted on the beam directly, there is no need to add 15cm to the top.
If there is no beam, the blinds will be mounted 15cm or more from the top of the window.
Curtain quick measure guide
For curtain width, generally it will be from wall-to-wall. You can easily estimate the width from the floorplan.
For HDB beam-to-floor, the height is usually 2.1m to 2.23m approximately.
For HDB ceiling-to-floor, the height is usually 2.4m to 2.7m approximately.
For Illustration: Curtain Width = Wall-to-Wall Width
Curtain Height (beam) = Beam to Floor Height
Curtain Height (ceiling) = Ceiling to Floor Height
Note: For both HDB & Condos, as long as the required height is not more than 2.5m, it won’t affect the price. This also depends on the type of fabrics chosen.
P.S. For curtain, normally it will be done from beam-to-floor to save some floor space.