This free caulk calculator tells you how many tubes of caulk or sealant to buy for a joint of any length. Enter the joint length, bead width and depth, pick a tube size, and get a rounded-up tube count with waste included.
Enter the total length of all joints you plan to seal, then the width and depth of the bead or joint. Choose a rectangular joint for gaps between two surfaces, or a triangular fillet bead for inside corners and trim edges. The calculator returns the number of tubes to buy (always rounded up), the sealant volume, how many feet one tube covers, and a comparison across every common cartridge size.
Running out of caulk halfway along a joint is more than an annoyance. A second tube from a different batch can differ slightly in color, and a bead that stops and restarts creates a weak spot where moisture can get in. Buying too much isn't free either: at $6 to $12 per cartridge, an oversized estimate on a whole-house re-caulk adds up, and opened silicone or polyurethane cartridges often skin over in the nozzle within days.
The numbers surprise people. A standard 5-foot bathtub has roughly 10 feet of tub-to-wall joint, so one cartridge is plenty. Ten windows with 14 feet of perimeter each is 140 feet; at a ¼ in × ¼ in bead that's about six cartridges, but at a ½ in × ½ in bead it jumps to nearly 25. Bead size matters far more than most people expect because volume grows with both width and depth. Contractors, property managers, and DIYers use this kind of estimate to price bids, prepare shopping lists, and avoid last-minute hardware store trips.
The calculator uses straightforward volume math:
Net volume (in³) = width × depth × length × shape factor
The shape factor is 1 for a rectangular joint and 0.5 for a triangular fillet bead, because a right triangle holds half the volume of the rectangle around it. Volume is converted to milliliters (1 in³ = 16.387 mL), then your waste allowance is added: Total mL = net mL × (1 + waste %). Tube volume comes from the printed fluid ounces (1 fl oz = 29.5735 mL). Finally, Tubes = Total mL ÷ tube mL, rounded up to the next whole tube.
Coverage per tube is rounded down so you never overestimate. Depth guidance follows the common industry rule of thumb that sealant depth should be about half the joint width, typically ¼ to ½ in, as discussed in ASTM C1193 (Standard Guide for Use of Joint Sealants). Product data sheets and local codes vary and take priority. This is a planning estimate, not engineering, permit, or inspection approval. Fire-rated joints and penetrations require a listed firestop system, not ordinary caulk.
You're sealing 60 feet of joints with a rectangular bead ½ in wide and ¼ in deep, using 10.1 fl oz cartridges and a 10% waste allowance.
One tube covers about 12.1 feet before waste and about 11 feet after it. At $7.50 per tube, the job costs about $45.00. With 20 fl oz sausage packs you'd need 3.
| Joint size (in) | Feet per tube |
|---|---|
| 1/8 × 1/8 | 97.2 |
| 1/4 × 1/4 | 24.3 |
| 1/2 × 1/4 | 12.1 |
| 3/8 × 3/8 | 10.8 |
| 1/2 × 1/2 | 6.0 |
A standard 60-inch tub has about 10 feet of tub-to-wall joint, plus a few feet of vertical corners. One 10.1 fl oz cartridge usually covers it at a ¼ in bead, even with a waste allowance.
It depends on bead size. A 10.1 fl oz cartridge covers about 24 feet of a ¼ in × ¼ in joint but only about 6 feet of a ½ in × ½ in joint. The calculator shows coverage for your own settings.
Plan for 10 to 15% extra for tooling, nozzle priming, and the leftover in the cartridge. Use 20 to 30% for porous surfaces such as stucco or rough brick, or for jobs with many short runs and corners.
Caulk is generally a lower-movement product (such as acrylic latex) for filling small gaps. Sealant (silicone, polyurethane, hybrid polymers) is built to stay flexible in joints that expand and contract. Both come in the same cartridge sizes, so the volume math is identical.
Yes. A fillet bead with equal legs fills half the area of the square around it, so the volume is half. Real beads are often slightly convex, which is why the waste allowance matters.
Sometimes. Silicone and polyurethane tend to skin over in the nozzle, and a plug of cured material often blocks the next use. Latex caulk keeps better if the nozzle is sealed, but plan on finishing the cartridge within a few weeks.
Calculator by Toolwick