# Sealant coverage: cartridges per 100 m of joint

> Work out sealant coverage from joint width and depth: ml per metre, cartridges per 100 m, and the waste allowance that stops a job running short.

Updated: 2026-11-12 · Source: https://karmindadhesive.com/resources/sealant-coverage-per-metre/

The question arrives as "how many cartridges for 100 m?" and the honest answer is that length does not decide it — the joint section does. Two jobs of the same length can differ by a factor of five in sealant, and the difference is entirely in width and depth.

## The arithmetic, in one line

Volume equals width × depth × length. Work in millimetres and the answer comes out in millilitres per metre directly, because 1 ml = 1,000 mm³:

```
10 mm wide × 10 mm deep × 1,000 mm long = 100,000 mm³ = 100 ml per metre
```

That is the whole calculation. Everything else is packaging.

## Coverage by joint size

| Joint (width × depth) | ml per metre | Metres per 310 ml cartridge | Metres per 600 ml sausage |
|---|---:|---:|---:|
| 6 × 6 mm | 36 | 8.6 | 16.7 |
| 10 × 10 mm | 100 | 3.1 | 6.0 |
| 12 × 12 mm | 144 | 2.2 | 4.2 |
| 20 × 10 mm | 200 | 1.6 | 3.0 |
| 25 × 12 mm | 300 | 1.0 | 2.0 |
| 30 × 15 mm | 450 | 0.7 | 1.3 |

The 310 ml figure uses 310 ml of nominal capacity; in practice a cartridge holds about 300 ml of usable sealant after the dead volume in the nozzle and the follower.

## Worked example: 100 m of a 10 × 10 mm joint

- Volume: 100 m × 100 ml/m = **10,000 ml = 10 litres**
- Cartridges of 310 ml: 10,000 ÷ 300 usable = **34 cartridges**, so 3 cartons of 12
- Sausages of 600 ml: 10,000 ÷ 600 = **17 sausages**, one carton of 20
- 200 L barrel: 10,000 ÷ 200,000 = **0.05 of a barrel** — the wrong format for this job

The same 100 m in a 25 × 12 mm joint is 30 litres, or 100 cartridges. That is why the question "how many cartridges per 100 m" cannot be answered without the section.

## Waste: the number that makes a job run short

Allow 5–10% on straight runs. Add more where:

- corners and changes of plane break the bead,
- the joint is overfilled and tooled back,
- the substrate is rough (concrete block, spalled edges),
- the gun leaves a slug in the nozzle at every stop.

On a first order, round up to the next carton. A second shipment of three cartridges costs more in freight than the three cartridges cost.

## When to move up a pack format

| Volume needed | Sensible format |
|---|---|
| Under 10 L | 310 ml cartridges |
| 10–100 L | 600 ml sausages |
| 100–500 L | sausages, or a 20 L drum where the grade allows |
| Above 500 L | 200 L barrel and a bulk gun |

The break-even is not only price per litre. A barrel needs a bulk gun, a clean line and a crew that will use it within the working time; a cartridge needs a gun that costs a tenth as much and can be handed to anyone.

## What this means for buyers

Send the joint section and the run length, not just the litres. A supplier who quotes cartridges without asking for width and depth is quoting a guess. If the job is quoted in litres, ask for the pack split — 10 litres is 34 cartridges, 17 sausages or a tenth of a barrel, and the freight and handling differ for each.

## Evidence note

The coverage figures are arithmetic from joint geometry; the 5–10% waste range and the usable volume of a cartridge are workshop estimates. Measure one bead on site and weigh it if the job is large enough for the difference to matter.