CalcCoverageA bead is a volume, not a line
Caulk is sold by the tube and spent by the inch of joint, and the two meet in a volume: the bead's cross-section — width × depth — times the total length of joint. That is the whole calculation, and it is why bead size matters more than length does. Double the width and the depth and the same tube covers a quarter as much joint, which is how a bathroom's worth of caulk disappears into one wide exterior gap.
Coverage per tube, by bead size
These are the published coverage figures for a standard 10.1 fl oz (300 ml) cartridge — the same arithmetic the calculator runs, printed so the shelf label can be cross-checked before the tube is in the gun.
| Bead width × depth | Linear feet per tube | Typical joint |
|---|---|---|
| 1/8 × 1/8 in | ≈ 97 ft | Fine cosmetic lines, trim paint lines |
| 1/4 × 1/8 in | ≈ 48 ft | Tub and shower edges on backer rod |
| 1/4 × 1/4 in | ≈ 24 ft | The standard bathroom and window joint |
| 1/2 × 1/4 in | ≈ 12 ft | Wide joints, correctly proportioned |
| 3/8 × 3/8 in | ≈ 11 ft | Exterior gaps |
| 1/2 × 1/2 in | ≈ 6 ft | Large uneven gaps — rod first, then reconsider |
Depth is the quiet half of the bead
Sealant is meant to flex, and it flexes correctly at a depth of about the width on narrow joints and half the width on joints wider than about 1/4 in — the hourglass shape a tooled bead takes over backer rod. A deep, fully filled joint is not stronger; it is stiffer, tears sooner, and quietly doubles the tube count. For any joint deeper than about 1/2 in, push in foam backer rod to set the depth and let the calculator's shallower depth figure do the rest — the rod costs less than the sealant it displaces, and the joint lasts longer for it.
Tube sizes, briefly: the 10.1 fl oz cartridge (labelled 300 ml in metric markets — the same tube) is the caulk-gun standard; 5.5 fl oz squeeze tubes suit one small job with no gun; 20.1 fl oz sausage packs feed a barrel gun on big exterior work and hold almost exactly two standard cartridges of sealant.