Outdoor blinds are cut to your opening, so the measurement decides everything. Take ten minutes, use a tape measure, and you avoid the single most common problem in this category: a blind that is 2 centimeters too narrow, letting wind whistle through the gap. This guide covers the exact steps for front and side mounting, plus the mistakes that cause most reorders.
Our made-to-measure outdoor blinds
What you need
A metal tape measure, a step stool if the opening is tall, a pen, and your phone for photos. Metal tape, not fabric: fabric tapes bow and can read long on wide openings. Photos help if you later want the supplier to confirm the fit, and most will happily check before cutting.
Step 1: Measure the width three times
Outdoor openings are rarely square. Posts settle, pergolas get built slightly out of plumb, and walls bow more than people expect.
Measure the width at the top, the middle, and the bottom of the opening. Write down all three numbers and use the smallest one. A blind cut to the largest figure will jam at the narrow point; cut to the smallest, it clears the full run.
Measure the width at the top, middle and bottom, and the drop on both sides. Use the smallest width and the longest drop.
Step 2: Measure the drop on both sides
Measure from the top of the opening down to the floor or rail on the left side, then again on the right. If the two differ, use the longer figure for the drop: a bottom rail resting slightly lower is fine, but a blind that stops short leaves a gap at the bottom that wind and rain love.
Step 3: Check whether the opening is square
Measure diagonally, corner to corner, both ways. If the two diagonals differ by more than about 1 centimeter, the opening is out of square. That is not a dealbreaker, but the factory needs to know, because a straight-cut blind in a leaning opening will show a wedge-shaped gap on one side. Send the two diagonal figures with your order and the cut gets adjusted.
Front mount or side mount: the difference in measuring
Front mount means the track fixes onto the face of the wall, post or beam, with the blind covering the whole opening. Measure the opening, then add a few centimeters on each side if you want the panel to overlap the edges. Front mount is the easier choice when the opening is already tight, and it lets the blind clear window sills or rails that sit inside the space.
Side mount means the tracks run along the inside faces of the posts, and the blind fills the opening exactly. Measure the clear distance between the posts, at the top, middle and bottom as before. Side mount looks cleaner from the front because the rails hide behind the posts, and it is the standard choice inside pergola frames.
Front mount fixes the track onto the face of the structure; side mount runs it along the inside of the posts.
If the posts are thicker than the track is deep, side mounting usually works. If the posts are very thin steel, front mounting onto the face is often more secure, since there is less material to screw into.
Common mistakes, in the order they happen
- Rounding up. People add "a little extra for safety" on the width. The blind then jams at the narrowest point. Use the smallest measurement.
- Measuring the old blind instead of the opening. A replacement blind should match the opening, not the worn-out panel you are removing.
- One measurement per direction. Openings move between top and bottom more often than they look like they do.
- Forgetting the diagonal check. Ten seconds with the tape saves a wedge-shaped gap on a leaning porch.
- Measuring with the screen door open when the blind has to clear the door's track. Note anything at floor level that the bottom rail needs to clear, and mention it when ordering.
Before you order
Write the measurements down as width first, then drop, and label the unit, centimeters or inches. Take one photo straight on and one from the side. If anything about the space is unusual, an angled wall, a thick handrail, a sloping floor, send the photos with the order. Made-to-measure suppliers cut after your confirmation, and most problems in this category trace back to a measurement taken in good faith but sent in the wrong unit.
Frequently Asked Questions
How much smaller should the blind be than the opening? For side mount, the track needs a small clearance on each side to slide in, usually under a centimeter. The factory deducts this automatically when cutting to your figures, so send the real measurements rather than pre-shrinking them yourself.
Can I install the blind inside a pergola with sloped posts? Yes, if the slope is mild and the factory knows about it. Send the top and bottom widths plus the post angle in your photos. Steeply sloped posts sometimes suit front mount better, with the track following the wall instead.
What if my opening is slightly too big for the blind size I received? Do not shim the tracks with loose packers in a windy spot. Ask the supplier for the correct bracket or a small extension profile; a zip track system carries wind load into the frame, and that load is only as good as the mounting.