Advanced options
Buy one more tube than the maths says: running out mid-bead guarantees a visible joint. Bathroom/kitchen wants sanitary silicone (mould inhibitors); exterior frames want frame sealant; skirting and coving gaps want decorator's caulk (paintable, which silicone never is). Masking tape both sides + tooled with soapy finger = the professional line.
What The Sealant Calculator Works Out
- Tubes needed: joint length divided by the metres a 300ml cartridge covers at your bead size, rounded up, plus one spare. A tidy 6mm bead runs about 12m a tube, a generous 8mm bead 7m and a 10mm gap fill 5m, so a bath's 4m perimeter fits one tube with margin.
- Typical jobs: reference lengths for the common UK jobs (bath about 4m, shower enclosure 3m, worktop run 3-4m, window frame 4-5m) so you can add up a whole bathroom before shopping.
- Custom joint width and depth (advanced): type the real gap and the calculator works out millilitres per metre from the cross-section (width x depth x 0.8 for a tooled bead). Depth is the multiplier the tube's small print means by "depending on application"; joints over 10mm deep want foam backer rod first, both to ration sealant and because it should bond to two sides, not three.
- Cartridge size (advanced): switch between the 80ml squeeze tube, 300ml and 310ml cartridges and the 600ml pro sausage. The metres-per-tube figure and the table update to match.
- Spare tubes (advanced): the tradesman's rule is one more than the sum says, because a bead interrupted mid-run cures into a visible splice. Set it to zero if you are only topping up.
- Sealant volume (advanced): total millilitres, ml per metre and what will be left in the last tube. Half-used cartridges keep for a few weeks with a screw in the nozzle.
- Cost (advanced): tubes including spares x your price, and the cost per metre of joint. A 300ml cartridge of sanitary silicone is typically GBP 5 to GBP 10, decorators' caulk GBP 2 to GBP 5, MS polymer GBP 8 to GBP 15.
- Type and cure (advanced): which chemistry suits the job and how long it takes to skin and cure. Sanitary silicone for wet rooms, low-modulus for exterior frames, acrylic caulk where it must take paint (silicone never does, and a smear of it repels emulsion for years), MS polymer for the adhesive-sealant double act.
- Sundries (advanced): masking tape for both sides of every joint (the guaranteed straight line), a profiling tool or soapy finger, remover gel for the old bead and backer rod where the joint is deep. Fill the bath with water before sealing its rim so the joint cures at the loaded position.
- Bead size table (advanced): ml per metre, metres per tube and tubes for your length at seven common joint sizes, with cost if a price is entered. Cut the nozzle at 45 degrees to the bead width and release the gun's pressure before the end of the run.