Glass / Window Sizing Calculator

Glass is where construction math stops feeling like flat shapes and starts feeling surgical: the pane has to fit the exact revealed opening, weigh what the frame and hinge can carry, be thick enough not to bow, and be the right type for safety and energy. One pane can be a simple lite; a sash window, sidelight or a patio door is several panes summed into one order.

Glass / Window Sizing Calculator takes one or more windows - width, height and quantity each - sizes the glazed area, subtracts the edge clearance, and reports the total glass area, the estimated weight from the glass thickness, and a material cost that scales with the glass type you choose. Float, tempered, laminated, low-E, tinted and double-glazed units are covered in both metric and imperial units.

The estimate runs live as you type, with the working shown step by step, and a learning guide explains glass weight math, thickness selection, safety locations and how rough-opening measurement differs from finished glass size. Everything runs in the browser - nothing is uploaded.

• Multiple windows: Add as many width - height - quantity rows as you need, each counted toward the total glazed area.
• Glass sizing math: Edge clearance per side is deducted from the measured opening so the pane size is the true cut size.
• Glass types: Float, tempered, laminated, low-E, tinted and double-glazed units, each with its own cost factor and weight behaviour.
• Thickness wizard: 3–12 mm in quick presets, driving the weight per area automatically (2.5 kg/m2/mm).
• Weight estimate: Total glass weight in kilograms and pounds, with a per-pane reading if you want it.
• Area & span: Total square feet / square metres with the largest single pane flagged for deflection-minded planning.
• Waste allowance: Default 5 percent for cutting, tooling and edge losses, adjustable per job.
• Cost model: Per-area price with a glass-type multiplier, so float and thermal units are priced on the same job.
• Live estimate: Every number updates as you type, with the maths shown step by step.
• Export: Copy or download the full glass report as text, CSV or JSON.
• Learning guide: Weight tables, thickness guidance, safety locations and measuring tips.

1. Pick the unit system. Feet/inches or metres for all window dimensions and the price per area.
2. Set the edge clearance. Keep the default or match your glazing allowance for a true cut size.
3. Add each window. One row per opening type - width, height and how many of that window there are.
4. Choose the glass type. Float for plain lites, or tempered / laminated / low-E / tinted / double glazed for the job.
5. Pick the thickness. 3–12 mm presets; weight follows automatically from 2.5 kg/m2 per mm.
6. Set waste and price. Adjust the cutting allowance and enter your per square foot / metre glass price.
7. Read the estimate. Total area, largest pane, weight and cost appear instantly.
8. Review the working. The maths line shows how opening minus clearance becomes area.
9. Export the report. Copy or download as text, CSV or JSON for the glazier or your quote.
10. Check the guide. Weight tables, safety locations and measuring tips when sizes get serious.

Example 1 - Picture window. A fixed window 6 ft wide by 4 ft high, one pane of 6 mm float: area 24 sq ft, weight about 67 kg (24 ft2 x 6 mm x ~0.51 kg/ft2/mm) before waste.

Example 2 - Sash window. Two sashes in one rough opening, each 2.5 x 4 ft (10 sq ft each), 4 mm float: 20 sq ft total, roughly 23 kg and a modest cost for a standard lite.

Example 3 - Patio door. A sliding door with two lites of 3 x 6.5 ft each in 6 mm tempered: 39 sq ft and the doubled price factor of tempered glass, weight near 109 kg - a two-person lift.

Example 4 - Triple entry area. Front door (3 x 7 ft) plus two sidelights (1.5 x 7 ft each) at 6 mm low-E: 42 sq ft with the low-E cost factor, over 117 kg of strengthened glass.

Example 5 - Bathroom obscure. A 3 x 4 ft privacy lite in 4 mm laminated (one layer obscured): 12 sq ft, thin, tough and heavier than plain float of the same size.

• Know the area before you call the glazier: Square footage / square metres per opening so quotes can be compared on the same basis.
• Weight that drives handling: Lifting, hinge, and framing loads are planable when the total kilograms are on the page.
• Type-aware cost: Tempered, low-E and thermal units are priced with their real multipliers, not a single flat rate.
• Size math that respects reality: Edge clearance and waste keep the cut size honest against the measured opening.
• Metric and imperial: Switch units without converting a thing by hand.
• Explainable numbers: The working line shows opening, clearance, area and weight so nothing is a black box.
• Export-ready: Text, CSV and JSON reports drop straight into quotes and work orders.
• Free and private: No uploads, no accounts, no logging.