How to measure and estimate sealant
Start with the total joint length and actual bead cross-section, then compare the volume with the cartridge label.
Back to calculator ↑Measure the joint you will fill
Measure every run in metres and add the lengths. Record the sealant width and fill depth in millimetres. If the joint varies along its length, estimate each distinct section separately and add the material volumes before deciding what to buy. A single average can conceal a much wider section that consumes considerably more sealant.
Use the rectangular option when a groove is filled across its width and depth. Use the right-triangle option only for a genuinely triangular bead, such as a specified fillet. A rounded surface finish, a void behind the bead or a variable groove can change the real volume; the drawing is a measurement aid, not a joint specification.
Formula and worked example
For a rectangular section, millilitres equal length in metres × width in millimetres × depth in millimetres. This works because one metre times one square millimetre is one millilitre. For a right triangular section, halve that cross-sectional volume. Multiply by 1 plus the chosen waste percentage, divide by the stated millilitres per cartridge and round up to a whole cartridge.
Example: a 6 m rectangular joint, 10 mm wide and 10 mm deep, takes 600 ml geometrically. A 10% allowance makes 660 ml. With 300 ml cartridges, 660 ÷ 300 = 2.2, so buy three whole cartridges. The 900 ml purchased volume exceeds the estimate by 240 ml; it is not a prediction that exactly 240 ml will remain after installation.
Interpret the result
The result is a geometric estimate plus your chosen allowance, not a guaranteed yield for every product. Sika’s published consumption tables describe theoretical coverage and note that surface condition, groove variation, nozzle waste and application can change actual use. A small sample section can help you judge an awkward or rough joint before placing a large order.
The calculator does not design a movement joint or choose a sealant chemistry. Width, depth, backing rod, primer, curing conditions and substrate compatibility are product and site questions. Check the chosen product’s data sheet before application, particularly for wet areas, exterior exposure or moving joints.
Buying checks and common mistakes
Read the actual pack volume: 280, 300, 310 and 600 ml sizes produce different whole-pack counts. Check whether a cartridge or foil pack fits your applicator. The optional price is your own input; a blank price stays unknown, while zero means a known zero cost. Marketplace links are searches only, so confirm the listing and date of the stock.
Do not substitute nozzle diameter for the filled joint dimensions automatically. Do not add the same waste allowance again after rounding to whole cartridges. Keep length in metres and cross-section in millimetres as labelled; converting one dimension to the wrong unit creates a large error. For multiple profiles, calculate each run and add the required millilitres before final rounding.
Common questions
Why does a triangular bead use half?
A right triangle with the same width and depth has half the rectangle’s cross-sectional area. Apply this only when the actual bead has that shape.
Do I need a backing rod?
That depends on the joint and product guidance. Enter only the depth filled by sealant, excluding the space occupied by backing rod.
Should I buy more than the result?
Enter a suitable allowance first, then use the whole-cartridge result. Irregular joints may call for a larger site-specific allowance.
Sources and calculation guidance
Check these against your chosen product’s label and instructions.