How much caulk you need
The amount of caulk depends on the volume of the joints you fill: their total length times the cross-section of the bead.
- Cross-section = joint width × joint depth (half that for a triangular corner bead)
- Volume (in³) = length in inches × cross-section
- Tubes = volume × (1 + waste) ÷ tube volume, rounded up
A standard 10.1 fl oz cartridge holds about 18.2 cubic inches.
Worked example
You are sealing 100 ft of joints 1/4 in wide and 1/4 in deep with 10.1 oz tubes at $8, with 10% waste.
- Cross-section: 0.25 × 0.25 = 0.0625 in².
- Volume: 100 × 12 × 0.0625 = 75 in³, about 41.6 fl oz.
- Length per tube: 18.2 ÷ 0.0625 ÷ 12 = 24.3 ft.
- Tubes: 75 × 1.10 ÷ 18.2 = 4.5, so 5 tubes, or $40.
Linear feet per 10.1 oz tube
| Joint size | Linear feet |
|---|---|
| 1/8 × 1/8 in | about 97 |
| 1/4 × 1/4 in | about 24 |
| 3/8 × 1/4 in | about 16 |
| 3/8 × 3/8 in | about 11 |
| 1/2 × 1/4 in | about 12 |
| 1/2 × 1/2 in | about 6 |
Joint depth and backer rod
For joints wider than about 1/4 inch, the depth of the sealant should be about half the width, with a minimum of 1/4 inch. Push a foam backer rod into deep gaps first: it saves caulk and lets the sealant stretch between two sides only, so it does not tear as the joint moves.
Choosing the right caulk
| Type | Best for | Paintable |
|---|---|---|
| Acrylic latex | Trim, baseboards, small cracks indoors | Yes |
| Siliconized acrylic | General interior use, light moisture | Yes |
| 100% silicone | Tubs, showers, sinks, windows | No |
| Polyurethane | Exterior joints, concrete, siding | Yes, once cured |
| Hybrid polymer | Exterior and interior, many materials | Usually |
For a clean result
- Remove old caulk completely and clean the surface; silicone does not stick to old silicone.
- Tape both sides of the joint with painter’s tape.
- Cut the nozzle at 45°, slightly smaller than the joint width.
- Apply in one steady pass, pushing the bead into the joint.
- Smooth with a wet finger or a tool, then remove the tape right away.
Most caulks are dry to the touch within an hour but need 24 hours or more before contact with water.