Calculator
Example data table
| Case | Shape | Dimensions | Frame | Mullions | Qty | Net per window (m²) | Total with 5% waste (m²) |
|---|---|---|---|---|---|---|---|
| A | Rectangle | 1200 × 1500 mm | 50 mm | V:1 H:0, 30 mm | 8 | 1.3920 | 11.6920 |
| B | Circle | Ø 900 mm | 40 mm | V:0 H:0 | 4 | 0.4478 | 1.8810 |
| C | Trapezoid | Top 900, Bottom 1400, H 1200 mm | 50 mm | V:0 H:1, 25 mm | 6 | 1.2306 | 7.7538 |
Formula used
All lengths are converted to meters. Areas are calculated in square meters (m²), then converted to square feet (ft²) for convenience.
Effective dimensions subtract the frame on both sides: Weff=W−2F, Heff=H−2F.
- Rectangle: A = Weff × Heff
- Circle: A = π × (Deff/2)², where Deff=D−2F
- Triangle: A = 0.5 × Beff × Heff
- Trapezoid: A = ((Aeff + Beff)/2) × Heff
- Custom: input area directly in selected units squared.
Mullion footprint is approximated as rectangular bars laid over the effective glazing rectangle: Am = V×w×Heff + H×w×Weff − (V×H×w²). The last term avoids double-counting intersections.
Net area per window is Anet=(A−Am)×(P/100). Total is Atot=Anet×Q. Waste allowance is Atot×(1+W/100).
How to use this calculator
- Select the window shape and measurement unit.
- Enter dimensions from drawings or site measurements.
- Add frame deduction to estimate clear glass size.
- Enter mullion counts and width to subtract obstructions.
- Set glazing percentage for partial glazing situations.
- Choose quantity and optional waste allowance.
- Press Calculate to view totals and download files.
Glazing takeoff accuracy for façade packages
Glass quantities often drive lead time and cost on envelope works. This calculator converts window geometry into a repeatable glazing takeoff, separating gross area from deductions so you can reconcile drawings, schedules, and procurement sheets. Results are shown per window and as project totals, with metric and imperial outputs. For mixed elevations, repeat runs per type and keep exported files as a traceable takeoff record.
Frame deductions and tolerance control
For clear glass size, frame deduction is applied on each side, reducing effective width and height by 2F. Typical allowances range from 35–60 mm depending on system depth and gasket detail. When effective dimensions reach zero, the tool floors values at zero to prevent negative areas.
Mullion footprint and intersection handling
Internal mullions reduce glazing by their projected footprint. The deduction uses mullion width multiplied by the effective span, then subtracts the intersection area so crossings are not double-counted. Common mullion widths for estimating are 25–50 mm, but verify shop drawings for exact sightlines.
Glazing percentage for partial infill zones
If only part of an opening receives glass (spandrel backpans, frit bands, or vision zones), apply a glazing percentage. For example, a 90% factor accounts for opaque portions without redesigning geometry. Keep the factor close to schedule values to align with façade performance and cost reporting.
Waste allowance and procurement planning
Waste allowance adds contingency for cutting, edge damage, and breakage. Typical site allowances are 3–8% for standard panes, and 8–12% for complex shapes or constrained access. Use the export buttons to create a quick record for RFQs, batching plans, and material reconciliation.
| Input | Value | Output | Value |
|---|---|---|---|
| Rectangle | 1200 × 1500 mm | Net per window | 1.3920 m² |
| Frame | 50 mm each side | Qty, Waste | 8 windows, 5% |
| Mullions | V:1, width 30 mm | Total with waste | 11.6920 m² |
FAQs
1) Does this include glass thickness?
No. It calculates glazing area only. Thickness, laminate build-ups, and spacer sizes should be specified separately in your glazing schedule and procurement documents.
2) What frame deduction should I use?
Use the clear opening reduction from your window system detail. If estimating, start with 35–60 mm per side and refine after shop drawings confirm glazing pocket and gaskets.
3) How accurate are mullion deductions?
They are an estimating approximation based on mullion width and effective spans. It is suitable for takeoffs and comparisons, but final ordering should use manufacturer cut sizes and unitized panel layouts.
4) When should I use glazing percentage?
Use it for partial infill openings, such as vision zones within larger frames, spandrel areas, or decorative bands. Set the percentage according to elevation takeoffs or schedule notes.
5) What waste allowance is typical?
Many projects use 3–8% for standard rectangles. Increase to 8–12% for curved glass, tight tolerances, difficult access, or high breakage risk during handling and installation.
6) Can I export multiple different runs?
Exports download the most recent calculation. For multiple types, run each type and save the CSV/PDF with a unique filename, or copy outputs into a consolidated takeoff sheet.
7) Why do I need effective width/height in custom mode?
Custom mode accepts a direct area value. Mullion deductions need spans to estimate footprints, so effective width and height are required when you want mullions subtracted from a custom area.