How many metres does a sealant cartridge cover?

A standard 310ml cartridge covers approximately 8.5 linear metres with a 6mm x 6mm joint (36mm² cross-section). For a 10mm x 10mm joint, coverage drops to approximately 3.1 metres. Coverage varies with joint profile, technique and waste. Always buy 10-15% extra for waste and tool-up cuts.

What sealant should I use around windows?

For external window frame to wall joints, use a low modulus neutral-cure silicone sealant rated for external use. Internally, acrylic sealant is suitable and can be painted. For glazing bead to glass, use a low modulus silicone. Never use acid-cure silicone near sealed units as it can attack the edge seal.

What is the correct joint width and depth for window sealant?

For frame-to-wall perimeter sealing, a joint width of 5-10mm is typical, with depth equal to width (or half width for wider joints). Maximum joint depth should not exceed 12mm. A 6mm x 6mm joint is standard for most domestic window installations. Backing rod should be used for joints deeper than 12mm.

How long does sealant take to cure?

Silicone sealant typically skins over in 10-20 minutes and achieves handling cure in 24 hours. Full cure takes 3-7 days depending on joint depth, temperature and humidity. At temperatures below 5°C, curing slows significantly. Low modulus silicones generally cure faster than high modulus types.

Do I need to use primer before applying sealant?

Modern silicone sealants generally do not require primer on clean, dry surfaces such as uPVC, glass and smooth masonry. However, primer is recommended on porous substrates like rough-cut stone, unpainted timber and some renders. Polysulphide sealants almost always require primer for adhesion. Always check the sealant manufacturer data sheet.

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Sealant Calculator — Cartridges for Window & Door Installation

Calculate the number of sealant cartridges needed for window and door installations. Covers frame-to-wall sealing, glazing bead sealant and expansion joints.

Number of Windows/Openings

Total windows and doors to seal

Average Frame Perimeter

2 x (width + height) of frame

Joint Width

Width of sealant bead

Joint Depth

Depth of sealant in the joint

Sealant Type

Match sealant to application

Application

Type of sealing work

How We Calculate This

This calculator determines the volume of sealant required and number of cartridges based on joint dimensions and total linear metres.

The formula

Volume per metre = Joint width (mm) × Joint depth (mm) × 1000 ÷ 1000 = ml/m

Total volume = Volume per metre × Total linear metres

Cartridges = Total volume (inc. waste) ÷ 310 ml

Typical joint sizes

Window frame to wall: 6mm x 6mm
Glass to glazing bead: 3mm x 3mm
Door frame to wall: 8mm x 8mm
Expansion joint: 10mm x 10mm+

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.