Window Blinds Measuring & Ordering Hub

Ordering blinds begins with which surface carries the brackets. Inside-mount treatments sit in the recess and depend on its usable width and depth. Outside-mount treatments cover an opening from the wall or trim and depend on overlap, headrail position and bracket support.

The same window can accept either style, but the measurements are not interchangeable. Do not buy from a generic calculator output alone: window-covering manufacturers often use their own order-width, factory-clearance and finished-fabric conventions.

Repair before replacement: vane, tilt and roller-shade decisions

Mounting measurements and mechanical repair are different tasks. For a damaged or stuck window treatment, identify its control type and failure mode first. Only if replacement is needed should you use the measuring instructions for the exact new product.

Before touching any controls, preserve cord and chain tensioners and verify whether the system is spring, cordless, chain-operated or motorized. Measure installed vane headrail-to-bottom drop only if the supplier actually requests that value. A made-up “standard deduction” may cause a return or a safety problem.

First identify the exact shade or blind

A product's name is not enough to choose a height rule or deduction. Blinds.com's published wood-blinds guide and roller-shades guide explain different ways to take and use recess measurements.

If vendor documents disagree for the exact shade, stop before ordering and request clarification for the SKU. Our blind helper stores the readings and shows method-specific references, but does not certify an order.

Inside mount or outside mount?

If your opening narrows from top to bottom, do not average away the narrowest width. If cranks, handles, tile or trim interfere, mark where the headrail will actually sit. For outside mounting, inspect whether the wall or trim can support the manufacturer's brackets.

Before measuring: which mount belongs on this window?

Our inside-mount versus outside-mount decision guide compares usable recess depth, obstruction clearance, side light gaps, bracket support and three worked examples. A window that looks square in a photo can still have three different widths; decide the mounting reference before entering a vendor order size.

A reliable measurement routine

1. Make a separate record for each window—even windows beside each other can differ.
2. Check whether the manufacturer labels ordering dimensions as finished fabric, headrail or overall covering sizes.
3. For inside mounting, record widths at the top, middle and bottom; heights at left, center and right; and the clear usable mounting depth.
4. For outside mounting, first decide the top bracket location, side overlap and desired lower coverage. Then calculate total intended area without calling it the final order size.
5. Review the exact product's height and width rules. Some products use the longest height; others, including certain vertical and banded treatments, can use the shortest.
6. Check whether the factory makes width deductions. Do not subtract clearance twice when the instructions specify the factory will do so.
7. Record any window handle, trim corner, radiator or door swing that changes the installation plan.

Match the measuring rule to the exact product — not just the word “blind”

Blinds.com publishes both a general measuring hub and a separate roller-shade guide. A narrower top measurement can be relevant for the roller-shade workflow, while traditional blinds often require the smallest of top/middle/bottom widths. Those methods describe the vendor's specific instructions, not a rule for every product with that name.

Stop if the product PDF conflicts with a generic vendor page. Keep both observed heights in the worksheet; ask the seller which applies to your SKU. Use the inside-mount helper to record measurements, not to certify an order.

Worked example: the product rule matters

Suppose a recess measures 35 1/8, 35 and 35 1/16 inches wide, and 58, 58 1/8 and 58 inches high. The width record's minimum is 35 inches; the height record's minimum is 58 inches and maximum is 58 1/8 inches. A product using longest-height ordering would use a different height than one using shortest-height ordering. Check its own measuring guide before placing the order.

For outside mount, a 36-inch opening with 2 inches of overlap on each side yields 40 inches of intended coverage. Adding 3 inches above and 2 inches below a 48-inch-high opening yields 53 inches of intended height. Those are geometry measurements, not necessarily the vendor's order form values.

Free tools for your worksheet

Use our inside-mount helper to compare multiple readings, outside-mount coverage planner for overlap arithmetic, and printable project worksheet for a take-to-store record.

Manufacturer reference

The LEVOLOR PREMIER January 2025 general measuring guidelines describe product-category exceptions, minimum mounting concerns and manufacturer deductions. They are a real maker's reference, not a universal rule for competing products. Always consult the exact model instructions and check child-safety requirements, particularly for older corded treatments.