Estimate how many tubes of seam compound a laid deck needs. Enter the seam length — or the deck area and plank width — the seam width and depth, and the cartridge size.
Use this when re-caulking a teak or other laid deck, a cockpit sole, or a swim platform, and you want to order the right number of tubes before reefing out the old compound.
Measure a typical seam’s width and the depth you will fill above the bond breaker or backing. If you do not want to measure every seam, estimate the total length from the deck area and the plank pitch (plank width plus one seam).
Check the cartridge label for its volume. Many seam compounds come in tubes of about 290–300 mL (about 9.8–10.1 US fl oz), but sizes vary.
Each seam is a long rectangular channel. Its volume is length × width × fill depth. Converting cubic inches to fluid ounces (1 US fl oz = 1.8047 in³), adding a waste allowance, and dividing by the cartridge size gives the number of tubes, rounded up.
When the seams are too many to measure, total seam length is about the deck area divided by the plank pitch: each plank-plus-seam strip of deck carries one seam along its length. Margin boards, king planks, and nibbed ends add some extra, which the waste allowance helps cover.
seam length (ft) = measured, or deck area (ft²) × 12 / plank pitch (in)
volume (in³) = length × 12 × width × depth
fl oz = in³ / 1.8047 × (1 + waste%)
cartridges = ceil(fl oz / cartridge size)
Each row below starts from the default inputs and changes only the columns shown. Recompute any row by hand with the formula above.
| Mode | Width | Depth | Tube oz | Seam ft | fl oz | Tubes |
|---|---|---|---|---|---|---|
| Measured | 0.25 | 0.375 | 10 | 400 | 274 | 28 |
| Measured | 0.1875 | 0.375 | 10 | 400 | 206 | 21 |
| Measured | 0.25 | 0.25 | 10 | 400 | 183 | 19 |
| Area | 0.25 | 0.375 | 10 | 533 | 366 | 37 |
| Area | 0.25 | 0.375 | 10 | 360 | 247 | 25 |
| Measured | 0.3125 | 0.5 | 9.8 | 250 | 286 | 30 |
With the calculator defaults (Seam length from = Measured; Total seam length (ft) = 400; Seam width (in) = 0.25; Seam fill depth (in) = 0.375; Waste allowance (%) = 10; Cartridge size (US fl oz) = 10), the arithmetic runs like this:
volume = length × 12 × width × depth = 400 × 12 × 0.25 × 0.375 = 450.0 in³
fluid ounces = in³ / 1.8047 = 249.4 fl oz; with 10% waste = 274.3 fl oz
cartridges = ceil(274.3 / 10) = 28
Result: 28 cartridges. 400 ft of seam at 0.25 × 0.375 in needs about 274 fl oz (8.11 L) including waste, in 10 fl oz tubes.
Now change Seam length from to Area and leave everything else alone:
seam length = area × 12 / plank pitch = 100 × 12 / 2.25 = 533 ft
volume = length × 12 × width × depth = 533 × 12 × 0.25 × 0.375 = 600.0 in³
fluid ounces = in³ / 1.8047 = 332.5 fl oz; with 10% waste = 365.7 fl oz
cartridges = ceil(365.7 / 10) = 37
Result: 37 cartridges. 533 ft of seam at 0.25 × 0.375 in needs about 366 fl oz (10.82 L) including waste, in 10 fl oz tubes.
Estimating from 100 ft² of deck with a 2-1/4 in plank pitch gives about 533 ft of seam — a third more than the measured 400 ft — and the tube count rises with it. If the two methods disagree badly, measure a few seams to check the plank pitch.
Fill depth is usually controlled by a bond breaker tape or backing in the bottom of the seam, so the compound sticks to the two plank edges but not the bottom. Measure the depth above that, not the full depth of the groove.
Seams opened up by reefing are often wider than the original. Measure after the old compound is out and the edges are cleaned, and use an average of several seams.
Order a few more tubes than the arithmetic says if the product is hard to find locally. A stalled job with half a deck caulked and a week’s wait for compound is worse than a spare tube on the shelf.
Units: Feet for seam length, inches for width, depth, and plank pitch; US fluid ounces for tubes.
Where the model stops: Uniform rectangular seams. Tapered seams, nibbing, margin details, and primer use are not modeled; the waste allowance covers overfill and tooling.
Not a substitute: Follow the seam compound maker’s joint-size, primer, and cure instructions.
| Seam width × depth | fl oz | Cartridges |
|---|---|---|
| 0.1875 × 0.25 in | 34.3 | 4 |
| 0.25 × 0.25 in | 45.7 | 5 |
| 0.25 × 0.375 in | 68.6 | 7 |
| 0.3125 × 0.375 in | 85.7 | 9 |
| 0.375 × 0.5 in | 137.1 | 14 |
Scale by your seam length: 400 ft is four times the fluid ounces. Round the cartridge count up after scaling, not before.
Two-part and some one-part seam compounds and their primers give off solvent vapour; work with ventilation and gloves. Dust from sanding cured compound and teak is an irritant; wear a dust mask and eye protection.
Measure across several planks and seams from the edge of one plank to the same edge of a plank several courses over, then divide by the number of courses. That averages out small variations.
Yes, if you are measuring seam length directly. In area mode they are not counted, so add a little waste.
Check the label. Many are about 290–300 mL; some marine products come in larger sausages or smaller tubes.
Compound is usually applied over a bond breaker, so only the depth above it gets filled.