Sealant Coverage Calculator
Buying too few sealant cartridges means a mid-job trip to the shop with a half-finished bead drying out, while buying too many wastes money on cartridges that will likely go hard before you need them again. Enter your total bead length and width below to get an accurate cartridge count.
Work out how many sealant cartridges you need
Enter your total bead length and the bead width you plan to apply.
A single cartridge at a 6mm bead width covers approximately 11.0m. For your total run, you'll need:
1 cartridge
Tip: buy one extra cartridge on top of this to allow for mistakes, wastage at the start and end of a bead, and touch-ups.
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A few well-reviewed sealants and adhesives.
£10.54
Pros
- 100% waterproof bond suits indoor and outdoor repairs
- Expanding polyurethane formula fills gaps in porous materials
- Bonds wood, stone, metal, ceramics and more
Cons
- Expands as it cures, so excess needs cleaning up before it sets
£4.93
Pros
- Meets EN15651 standard for sanitary and facade sealing applications
- Anti-fungal formula resists mould around baths and sinks
- Waterproof cure suits both interior and exterior use
Cons
- Needs a standard cartridge gun, sold separately
£6.50
Pros
- Instant grab bonds wood, ceramic, metal and more without mechanical fixings
- Water-based formula is low odour for indoor use
- Well-known high-street brand widely stocked for top-ups
Cons
- Slower full cure time than a two-part epoxy for heavy loads
Frequently asked questions
How much sealant does one cartridge cover?
It depends on the bead width you apply. A standard 310ml cartridge covers a longer run at a thin 3mm bead than it does at a thicker 10mm bead, since a wider bead uses far more volume per metre of length.
Should I round up or down when buying cartridges?
Always round up to the next whole cartridge. Sealant left over in an opened cartridge often dries out before your next job, but running short mid-bead means an unsightly join, so it pays to have a little extra on hand.
What bead width should I use around a bath or shower tray?
A 5-6mm bead is typical for baths, shower trays and worktop joints, giving enough flex to cope with movement without looking bulky. Wider gaps or corners may need a slightly thicker bead to fill properly.
Why should I buy a spare cartridge?
Sealant is fiddly to apply neatly, and a shaky first attempt, an air bubble, or a nozzle that tears the bead can waste more than you expect. Having one spare cartridge means you can redo a section without a trip back to the shop.
How this calculator works
This calculator uses a simple formula: Volume of Sealant = Bead Length x Bead Width x Sealant Coverage Rate. The ‘Bead Length’ and ‘Bead Width’ are entered in centimetres, reflecting the total length and width of the joint you intend to seal. The ‘Sealant Coverage Rate’ is expressed as square metres per cartridge – this figure varies significantly depending on the sealant type and manufacturer, so it’s vital to check the product information before using the calculator.
Sealant Types & Typical Coverage Rates (UK)
- **Polyurethane Sealants:** Often provide 3 - 6 square metres per 280g cartridge (£7.99 – £14.99). Excellent for external use and larger gaps, like around window frames.
- **Silicone Sealants (Neutral Cure):** Typically offer 2 - 4 square metres per 280g cartridge (£6.49 – £12.99). Ideal for bathrooms and kitchens due to their mould resistance.
- **Silicone Sealants (Sanded/Unsandered):** Coverage rates vary from 1.5 - 3 square metres per 280g cartridge (£5.99 - £11.99), suitable for smaller jobs and interior applications. Always check the manufacturer's guidelines.
- **Acrylic Sealants:** Generally provide around 4-6 square metres per 280g cartridge (£7.49 - £13.99). Often used for interior woodwork and gaps.
Worked example: Sealing a Window Frame
Let's say you’re sealing the exterior of a window frame with a polyurethane sealant. You measure the gap to be 1.8m long and 0.15m wide (total bead length = 1.8m, bead width = 0.15m). The manufacturer states that this particular polyurethane sealant offers a coverage rate of 4 square metres per cartridge. Inputting these values into the calculator yields: Volume of Sealant = 1.8m x 0.15m x 4 sq m = 1.08 cubic metres.
This equates to approximately 1.08 litres, which would likely require purchasing one 1 litre cartridge (£7.99). It’s always best to slightly overestimate, especially for external applications where weather exposure is greater.
More questions answered
What units should I use?
The calculator uses centimetres (cm) for length and width, and square metres (sq m) for area. Ensure you're consistent with your measurements – converting between metric units is easy!
Can I use this calculator for a small gap?
Yes, absolutely! Even small gaps benefit from sealant to prevent drafts and water ingress. Just ensure you measure the dimensions accurately; even a tiny gap can require a significant amount of sealant.
What if my gap isn't perfectly rectangular?
While the calculator works best with rectangular shapes, you can approximate by measuring the longest dimension and using it for both length and width. For irregular shapes, consider dividing them into simpler sections to calculate the area more accurately.
How does the sealant coverage rate affect the result?
The coverage rate is a crucial factor – different sealants have vastly different efficiencies. Always refer to the manufacturer's specifications on the product packaging before using the calculator.
Should I round up or down when buying sealant?
It’s generally better to slightly overestimate rather than underestimate, especially for exterior projects. A small surplus is often preferable to running out mid-job.
What if I need to apply multiple coats of sealant?
The calculator calculates the volume needed for a single coat. If you plan on applying two or more coats, multiply the result by the number of coats (e.g., 2 coats x 1.08 cubic metres = 2.16 cubic metres).
Does this calculator account for wastage?
No, the calculator provides a theoretical volume based on the bead length and width. It doesn't factor in potential wastage due to application errors or sealant shrinkage. Allowing for an extra 10-20% is advisable.
What if I’m using a different type of sealant?
The calculator will only provide accurate results if you use the correct coverage rate for your specific sealant. Always check the manufacturer's guidelines on the product packaging before proceeding.
Is this calculator suitable for large-scale projects?
For very large areas, it’s recommended to calculate the total area manually and then adjust the sealant volume accordingly. The calculator is best suited for smaller, more manageable jobs.
Where can I find the sealant coverage rates?
The coverage rate should be clearly stated on the manufacturer's product packaging – look for it in the technical specifications or on a label. Check Amazon UK listings for detailed product information before purchasing.