Inside mount: Track = Recess Width − Deduction − Trim.
Outside mount: Track = Face Width + (2×Overlap) + Returns − Trim.
If you join pieces, join loss = (Pieces−1)×Join Gap.
- Choose units, then select inside or outside mount.
- Enter your measured width of the opening.
- Set deduction for inside mounts if needed.
- Set overlap and returns for outside mounts.
- Adjust trim, rounding, and max piece length.
- Press calculate to see the result above.
| Scenario | Mount | Width | Overlap/Side | Returns | Deduction | Track (rounded) |
|---|---|---|---|---|---|---|
| Kitchen window | Inside | 180 cm | — | 0 cm | 0.6 cm | 179.2 cm |
| Patio door | Outside | 200 cm | 2.5 cm | 0 cm | — | 204.8 cm |
| Corner return | Outside | 160 cm | 3.0 cm | 10 cm | — | 175.8 cm |
Accurate width capture for smooth operation
Track sizing starts with a reliable width measurement taken at three points. For recess mounting, use the smallest width to avoid binding. Many installers target a 0.3–0.8 cm deduction so carriers glide freely. This calculator lets you set a deduction plus a trim allowance, then rounds to your shop’s cutting increment for consistent output.
Inside mount deduction and trim controls
Inside fits often require clearance for brackets, tile reveals, or slight out-of-square frames. A small trim allowance helps prevent end caps rubbing on paint edges. If your measured width is 180 cm and you apply 0.6 cm deduction and 0.2 cm trim, the raw track becomes 179.2 cm before rounding. Adjust values to match your hardware tolerances and measurement confidence.
Outside mount overlaps and returns for coverage
Outside mounting prioritizes light control and edge coverage. A common overlap is 2–5 cm per side, depending on window depth and stack. For corner windows, left and right returns extend the track around the wall to reduce gaps. The calculator adds both overlaps and returns, then subtracts trim so the finished length remains practical to install.
Joining sections and accounting for connector loss
Long runs may be shipped as multiple sections. Some joiners introduce a small lost length at each connection. Enter the number of pieces and the join gap per connection; the tool applies total join loss as (pieces−1)×gap. This prevents a finished run from coming up short after assembly, especially on multi-panel installations.
Rounding, split guidance, and export-ready outputs
Workshops often cut to fixed steps such as 0.1 cm, 0.5 cm, or 1 cm. Set the rounding step to standardize cutting lists. If a track exceeds your maximum manageable piece length, the calculator suggests an even split across multiple pieces and reports an approximate per-piece length. Export results as CSV for job sheets or PDF for client approvals and installation packs. Document your final number on-site, then verify clearance before ordering carriers and vanes always.
FAQs
1) What width should I enter for an inside mount?
Measure top, middle, and bottom, then use the smallest width. This reduces the chance of binding when frames are out of square or finished unevenly.
2) How much overlap is typical for outside mounts?
Many installations use 2–5 cm per side. Increase overlap for better light blocking or when the vane stack needs more clearance near trims and handles.
3) When should I use returns?
Use returns for corner windows, wrap-around coverage, or when you want the vanes to finish closer to the wall. Enter left and right returns separately for accuracy.
4) Why include a trim allowance?
Trim allowance is a small reduction to prevent end caps or carriers from rubbing on paint edges, tiles, or tight brackets. It helps achieve smoother movement over time.
5) What does join gap mean?
Join gap is the effective length lost at each connection when two track sections are joined. The calculator multiplies it by the number of joins to avoid a short final run.
6) How should I choose a rounding step?
Match your cutting tools and ordering rules. If your supplier cuts to 1 cm increments, use 1. If you can cut precisely, use 0.1 or 0.5 for tighter control.