Preparation
Decorator’s caulk or sealant cartridges per metre of joint
- where
- sealant per metre (ml/m)
- shape factor (0.5 triangular, 1 square)
- bead width (mm)
- bead depth (mm)
- metres per cartridge
- cartridge volume (ml)
- total sealant (ml)
- total length of joint (m)
- waste allowance (%)
- cartridges needed
Explain this equation
Works out how much caulk or sealant a job needs and how many cartridges to buy.
A bead is a long prism. Its cross-section is width times depth for a square joint, or half that for a triangular fillet in a corner. One millimetre squared over one metre is exactly one millilitre, so k b e is millilitres per metre. Cartridge volume divided by that is metres per cartridge. Total length times millilitres per metre, plus waste, divided by cartridge size gives cartridges.
Volume of a prism: cross-section times length.
Sense check: a 6 × 6 mm triangular bead uses 18 ml per metre, about 17 m per 310 ml cartridge; 30 m needs 2 cartridges.
Watch out: gaps are rarely even. Wider gaps use a lot more; consider backer rod in deep joints.
Works out cartridges of decorator’s caulk or sealant from the joint length and bead size.
Enter your values to see the result.
Good to know
A bead’s volume per metre is its cross-section: 1 mm² of section over 1 m is 1 ml. A square-section joint is width × depth (k = 1); a fillet in a corner, such as skirting to wall, is a triangle, half of width × depth (k = 0.5). Sika’s table gives 3.0 m per 300 ml cartridge for a 10 × 10 mm joint, which this matches. Most decorator’s caulk is 310 ml. Gaps wider than the product allows (often about 6–10 mm for acrylic caulk) should be packed or filled first.
Common mistake
Squaring the bead size in your head (“6 mm bead”) as if it were full section in a corner: a fillet uses half as much.
Limits
Even bead size. Real beads vary, and gun waste and nozzle trimming are covered only by the allowance.
Sources
- Sika NZ, Sealant consumption guide (10 × 10 mm joint: 3.00 m per 300 ml cartridge; figures approximate)
- Geometry: rectangle and cylinder surface areas, prism volumes
Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.