Caulk Calculator
A caulk calculator turns joint length, width, and depth into tubes. 40 ft of 1/4 × 1/4 in joint needs 2 tubes of 10.1 oz caulk, about 24.3 ft per tube.
Caulk calculator: tubes for a joint
A caulk calculator finds the volume of the joint and divides it by the volume of one tube. A standard 10.1 oz tube holds about 18.2 cubic inches. A 40 ft joint that is 1/4 in wide and 1/4 in deep holds 30 cubic inches. With 10% waste that is 33 cubic inches, so you need 2 tubes, and each tube runs about 24.3 ft.
The formula in plain words
Picture the joint as a long square rod of caulk. Its end is a small square. Its length is the run you measured. You work out the volume of the rod and see how many tubes fill it.
- Cross section = bead width × bead depth, in square inches.
- Joint volume = joint length in feet × 12 × cross section.
- Volume with waste = joint volume × (1 + waste percent ÷ 100).
- Tubes = volume with waste ÷ 18.2, rounded up.
- Feet per tube = 18.2 ÷ (cross section × 12).
The tube volume comes from 10.1 fluid ounces × 1.8047 cubic inches per fluid ounce, which is 18.23 cubic inches, rounded to 18.2.
Worked examples
These match the calculator exactly.
Example 1: 40 ft of joint, 1/4 in wide, 1/4 in deep, 10% waste.
- Cross section: 0.25 × 0.25 = 0.0625 sq in
- Joint volume: 40 × 12 × 0.0625 = 30 cu in
- With waste: 30 × 1.10 = 33 cu in
- Tubes: 33 ÷ 18.2 = 1.81, rounded up to 2
- Feet per tube: 18.2 ÷ (0.0625 × 12) = 24.3 ft
Example 2: 120 ft of joint, 3/8 in wide, 3/8 in deep, 10% waste.
- Cross section: 0.375 × 0.375 = 0.1406 sq in
- Joint volume: 120 × 12 × 0.1406 = 202.5 cu in
- With waste: 202.5 × 1.10 = 222.75 cu in
- Tubes: 222.75 ÷ 18.2 = 12.24, rounded up to 13
- Feet per tube: 18.2 ÷ (0.1406 × 12) = 10.8 ft
Feet per tube by joint size
| Joint (width × depth) | Feet per 10.1 oz tube |
|---|---|
| 1/8 × 1/8 in | 97.1 ft |
| 1/4 × 1/4 in | 24.3 ft |
| 3/8 × 3/8 in | 10.8 ft |
| 1/2 × 1/2 in | 6.1 ft |
| 1/2 × 1/4 in | 12.1 ft |
Coverage drops fast as the joint grows. Doubling both the width and the depth cuts the coverage to a quarter.
Square joint versus round bead
Caulk charts often list a round bead. A 1/4 in round bead has a cross section of π ÷ 4 × 0.25², which is 0.049 sq in. That gives 31 ft from an 18.2 cubic inch tube, close to the 30 ft Liquid Nails prints on its 10.1 oz tube. A gap in trim or a tub edge is closer to a filled joint than to a round string, so the calculator uses width × depth.
How to measure
- Measure the total length of every joint you plan to seal and add them.
- Measure the width of the gap at its widest typical point.
- Measure the depth the caulk will fill. Use a backer rod in deep gaps.
- For a bead on trim, a tub, or a sink, use the width of the gap and a depth equal to the width or a bit less.
Common mistakes
- Buying by tube count from the label without checking the bead size.
- Forgetting waste. The nozzle, the tube end, and tooling all take some.
- Filling a deep gap with caulk alone. It wastes sealant and fails sooner.
- Mixing joint sizes. Run the calculator once for each size and add the tubes.
- Using a 10.1 oz coverage chart for a different tube size.
Sources
- Liquid Nails, tub and tile acrylic latex caulk: 30 lineal feet per cartridge at a 1/4 in bead (liquidnails.com).
- Tube volume is 10.1 fl oz × 1.8047 cu in per fl oz, a unit conversion.
- Calculator.academy and other calculator sites list matching coverage by bead size, which we checked against the volume math.
Our feet per tube uses a full square joint and does not match a chart based on a round bead. Both are correct for their shapes.
Related calculators
Trim joints are covered by the baseboard calculator and the wainscoting calculator. Total up the joint lengths with the linear feet calculator.
Frequently asked questions
How much caulk is in a standard tube?
A standard cartridge holds 10.1 fluid ounces. At 1.8047 cubic inches per fluid ounce, that is about 18.2 cubic inches, and that is the volume the calculator uses.
How many feet does one tube of caulk cover?
It depends on the joint. A 1/4 × 1/4 in joint takes about 24 ft per tube. A 3/8 × 3/8 in joint takes about 11 ft. Liquid Nails rates its 10.1 oz tub and tile caulk at 30 lineal feet using a 1/4 in round bead, which is a bit more because a round bead holds less than a square joint.
Why does the calculator say 24 ft when the tube says 30 ft?
A label that says 30 ft at 1/4 in assumes a round bead. A round bead of 1/4 in diameter holds about 79% as much as a 1/4 × 1/4 in square joint. The calculator fills the full width and depth of the joint, which is the safer count for gaps.
How much extra caulk should I buy?
The calculator adds 10% for waste by default. Tooling, cutting the nozzle, and the tube end that never empties all use some. Raise it for rough surfaces or deep gaps.
How deep should a caulk bead be?
Match the depth to the width for a small joint. Wide gaps often use a backer rod so the sealant is thinner than it is wide. Follow the product label for the depth it allows.
Estimates only. Verify quantities with your supplier before purchasing.