Glass cost calculator — what fabricators need to know

Glass is the most consistently mispriced line item in fabrication quotes. Here is why and how to fix it.

Why glass is different

Unlike sections and hardware, glass pricing has non-linear thickness scaling:

• 5mm → 6mm: ~12% increase
• 6mm → 8mm: ~22% increase
• 8mm → 10mm: ~30% increase
• 10mm → 12mm: ~38% increase

And then tempering (heat treatment) adds 35–55% on top, regardless of thickness.

Single / Double / Tempered

| Type | Cost multiplier vs base 6mm clear | |---|---| | 6mm clear single | 1.0x | | 6mm tinted single | 1.15x | | 6mm tempered | 1.55x | | 6mm DGU (double glazed) | 2.4x | | 6mm tempered DGU | 3.4x | | 6mm Low-E DGU | 3.8x | | 6mm Low-E tempered DGU | 4.7x |

These are typical Indian market multipliers for residential glass in 2026. Commercial volume buyers can negotiate ~15% lower.

Color options

Tinted glass (green, blue, bronze, grey) usually adds 8–15% over clear of the same spec. Reflective coated adds 25–40%.

For a luxury client, mirror-coated black glass at 8mm tempered can be 6x the price of clear — make sure they sign off on the spec before ordering.

Silicone calculation

Almost everyone underestimates silicone. The formula:

Silicone (mL) = perimeter (m) * joint width (mm) * joint depth (mm) * 1.1

The 1.1 is the 10% waste factor — silicone hardens in the gun after pauses and you lose more than you think.

For a 1500mm x 1500mm window with 8mm joint width and 6mm joint depth:

perimeter = 6m
silicone = 6 * 8 * 6 * 1.1 = 316 mL

A 300mL cartridge does roughly one such window. Don't bid based on "1 cartridge for 2 windows."

DGU spacer & gas

For double-glazed units (DGU):

• Aluminum spacer: cheapest, slight thermal bridge
• Warm-edge spacer (Super Spacer, TGI): 12–20% more, better thermal performance
• Argon fill: ~₹120–180 per sqft, dramatically improves insulation

If your client specs "high-performance glass" without details, default to 6mm Low-E + 12mm argon + 6mm clear DGU with warm-edge spacer and disclose. It is the modern residential baseline.

What kills margins

The Low-E specification trap: client asks for "Low-E coating", you quote standard Low-E (soft coat), supplier delivers hard coat. They are 20% different in price and 40% different in performance.

Always specify the coating brand (Saint-Gobain Cool-Lite, AIS Ecosense, Modiguard) on the quote.

App helps

Window & Door Estimate Pro has the glass spec selector built in — pick thickness, type, color, and Low-E in 3 taps. Free on Google Play.