Silicone sealant calculator
How far a cartridge goes depends almost entirely on the joint width. Measure the joints around the bath, shower tray, worktop or windows and choose the width.
Your measurements
Result
- Sealant cartridges needed (300 ml)
- 2 pcs
For a standard 300 ml cartridge; the joint depth affects real consumption.
How the calculation works
- A 300 ml cartridge covers about 12 m of 5 mm joint, about 7.5 m of 8 mm joint and about 6 m of 10 mm joint.
- Cartridges = total joint length ÷ metres per cartridge, rounded up.
Worked example
For 10 m of 8 mm joints (bath, shower and kitchen worktop): 10 ÷ 7.5 = 1.3, so 2 cartridges.
What the calculator assumes
- The joint is assumed to be about 5 mm deep; for deeper joints, put in a backer rod first.
When to adjust the result
- Sanitary silicone (with fungicide) is for bathrooms and kitchens; for window frames use neutral silicone or paintable acrylic.
- Silicone doesn't bond well to old silicone — remove it completely first.
- Joints wider than about 15 mm or with a lot of movement need a different product (polyurethane sealant, profile).
Applying silicone neatly
Remove old sealant completely, clean with alcohol and let the joint dry; silicone does not bond to old silicone. Mask both sides with tape, cut the nozzle at 45° to the joint width and run the bead in one steady movement.
Smooth the bead with a tool or a finger dipped in soapy water, then remove the tape straight away before a skin forms. Fill a bath with water before sealing it so the joint is not stretched later, and let the silicone cure for the time on the cartridge before showering.
Frequently asked questions
How far does a tube of silicone go?
About 6–12 m from a 300 ml cartridge, depending on the joint width (10 mm to 5 mm).
Silicone or acrylic?
Silicone for wet areas and joints that move; acrylic where you want to paint over it, such as around frames and skirting.
Silicone or acrylic sealant?
Silicone for wet areas and joints that move; acrylic for paintable joints along skirting, frames and plaster.
Why does bathroom silicone go black?
Mould grows on the surface when the bathroom stays damp; sanitary silicone with fungicide and good ventilation slow it down.