BLINDS / COVERAGE GEOMETRY
Outside-Mount Blind Coverage Planner
Estimate a covering's intended width and height from the opening and your chosen overlap. This is a geometry calculator—not a manufacturer's automatic order sizing tool.
Worked coverage example
For an opening 36 inches wide by 48 inches high with 2-inch overlap on each side, the intended covering width is 40 inches. If the covering starts 3 inches above and ends 2 inches below, intended overall height is 53 inches. Verify the vendor's exact product order rules; for instance the fabric and complete assembly may be different widths.
Coverage versus SKU order: three source-defined examples
The calculator deliberately returns a coverage goal, never an order recommendation. For its default 40-in desired fabric width, the corresponding ordering numbers could differ depending on the exact manufacturer document. The following are separate published configurations, not interchangeable order instructions.
| Document / configuration | Hypothetical order for 40-in fabric goal | How to use it |
|---|---|---|
| Blinds.com general outside-mount roller guide | 43 in (adds 3 in to desired fabric) | Only if your exact chosen product uses this bracket-to-bracket rule |
| Blinds.com no-valance roller fabric PDF | 41 3/8 in (fabric 1 3/8 in narrower) | Only if the SKU matches the named PDF construction |
| Blinds.com outside-mount cellular guide | 40 in (exact specified outside shade width) | Only under that cellular model's current order definition |
Example supplier question: “For this exact SKU and outside mount, does the entered width mean fabric, bracket-to-bracket or complete cassette? What is the current published fabric deduction?” Keep the answer, product model and bracket fixing-space check before purchasing. See the full width-convention comparison.
Limits
This tool does not verify wall strength, top-fixing space, obstructing handles, headrail stack, child safety, light gaps or bracket depth. Do not install into an unsupported surface. Keep shades and blind cords inaccessible to young children; use current compliant cordless options where appropriate.
Manufacturer source
LEVOLOR PREMIER January 2025 measuring guidelines (PDF, LPGI-19) describe general inside/outside mounting, overlap and ordering differences.
Before using planned coverage as an order
| Question to answer | Why the arithmetic cannot decide it |
|---|---|
| Is the specified width the headrail, entire assembly or fabric? | Hardware, clutch and brackets may make the fabric narrower than the order width. |
| Can the intended bracket position be fixed securely? | The calculator cannot see hidden services, trim thickness or a weak mounting surface. |
| Will the raised covering clear a handle, vent, door or other obstruction? | Coverage overlap is not a physical headrail or stack-height check. |
| Are side and bottom overlaps realistic for this window? | A sill, trim or adjacent wall may prevent the chosen values. |
Worked obstruction scenario
Two windows can both be 36 × 48 inches, with identical intended 40 × 53-inch coverage. One has an unobstructed wall above; the other has a projecting crank near the intended rail. The calculations match, but the second assembly may interfere with the crank or need a different mount. Mark the actual proposed headrail and fabric boundaries on a paper worksheet, then compare them with the manufacturer bracket diagram before ordering or drilling.
For any blind with cords or chains, follow the child-safety rules for your market; the U.S. CPSC recommends cordless coverings in homes with young children. This tool cannot certify child safety or wall-mount suitability.