Sealant Calculator
Find out exactly how many cartridges of sealant or silicone you need. Enter your joint lengths, bead size and cartridge volume to get the cartridge count, coverage and estimated cost.
Cartridges needed
For 6 m of joints (incl. 10% waste)
How this was worked out
Sealant volume equals the bead cross-section multiplied by the total joint length, plus your wastage allowance.
| Bead cross-section | 36 mm² |
| Total joint length | 6 m |
| Sealant needed (no waste) | 216 ml |
| With 10% wastage | 237.6 ml |
| Coverage per cartridge | 8.3 m |
Assumes a solid rectangular bead filling the joint. A tooled, concave finish uses a little less, so this gives a small built-in safety margin.
Quick tips
- • A standard cartridge is around 300 ml and covers roughly 8–12 m of a typical bathroom bead.
- • Measure the joint gap for width, and the depth of the gap for depth — deeper joints use much more sealant.
- • Always buy at least one spare cartridge; part-used tubes often set before a second job.
- • Use the right sealant: sanitary silicone for wet rooms, frame sealant for windows and doors.
Typical bead sizes
Good to know
Results are estimates for planning and shopping. Real usage depends on your bead technique, joint consistency and how much you tool away. Round up and keep a spare so you never stop a run halfway.
About the Sealant Calculator
The Sealant Calculator tells you how many cartridges of silicone or caulk to buy before you start a job. Instead of guessing and making a second trip to the shop — or throwing away half-used tubes — you enter the joints you need to seal, the size of the bead and your cartridge volume, and it works out the exact cartridge count, coverage per tube and estimated cost.
It works by treating each bead as a small rectangular channel: the cross-section (width × depth) multiplied by the total length of your joints gives the volume of sealant required. A wastage allowance covers offcuts, tooling and the sealant left in the nozzle, and the calculator divides the total by your cartridge size and rounds up to whole cartridges. Application presets set typical bead sizes for bathrooms, kitchens, windows and expansion joints, and you can switch between metric (mm, m, ml) and imperial (in, ft, fl oz) at any time.
How to Use the Sealant Calculator
- 1 Pick an application — bath, kitchen, window, expansion joint and more — to load a typical bead width and depth.
- 2 List your joints — add a row for each run and enter its length. Name them so the list matches your project.
- 3 Set the bead size — adjust the width and depth to match your actual joint if it differs from the preset.
- 4 Choose your cartridge size and wastage, and optionally add a price per cartridge for an instant cost estimate.
- 5 Read your results — cartridge count, total volume, coverage and cost update automatically as you type.
Frequently Asked Questions
How much does one cartridge of sealant cover? +
It depends entirely on the bead size. A standard 300 ml cartridge covers about 12 m of a 5 × 5 mm bead, but only around 3 m of a chunky 10 × 10 mm expansion joint. The calculator shows the exact coverage for your bead size in the results, so you can see how far each cartridge stretches.
What bead width and depth should I use? +
Width is the visible gap you're filling and depth is how far the sealant goes into the joint. For most bathroom and kitchen work a 5–6 mm bead is typical; windows and doors often need 8 mm, and movement or expansion joints can be 10 mm or more. Use the application presets as a starting point and measure your own joint if you're unsure.
Why should I add a wastage allowance? +
Some sealant is always lost — priming the nozzle, tooling away excess, uneven joints and the bit left in the tube when it sets. A 10% allowance covers most jobs; add more for wide joints, rough surfaces or if you're new to applying sealant. The calculator adds this on top before rounding up to whole cartridges.
What's the difference between silicone, caulk and sealant? +
"Sealant" is the general term. Silicone is flexible and waterproof, ideal for bathrooms, kitchens and anywhere that stays wet or moves. Acrylic caulk is paintable and better for gaps around skirting, coving and trim that you'll decorate over. This calculator works for any of them — just match the cartridge size to the product you buy.
Can I use it for expansion or movement joints? +
Yes. Pick the Expansion joint preset or set a wider, deeper bead to match your joint. Note that deep movement joints are often part-filled with a backer rod so the sealant only forms the top layer — if you use one, enter the sealant depth above the rod rather than the full joint depth.