About the Caulk Calculator
This caulk calculator estimates how many tubes of caulk or sealant to buy for a run of joints. Enter the joint width, the depth of sealant, the total length in feet and the tube size, and it returns the number of tubes, the volume of sealant and how many linear feet one tube will run for that bead.
It is useful for sealing windows and doors before painting, siding and trim joints, expansion joints in concrete, and tub or countertop seams. A standard 10.1 oz cartridge runs roughly 24 ft of a 1/4 × 1/4 inch bead but only about 6 ft of a 1/2 × 1/2 inch joint, so the joint size matters far more than people expect.
Choose a triangular (fillet) bead for inside corners where the sealant is tooled into a cove; it uses half the volume of a square joint with the same width and depth. Deep joints should be filled with backer rod first, which also keeps sealant from bonding to the bottom of the joint.
With the default inputs, the tubes needed is 5. Change any value above to recalculate instantly.
How to use the caulk calculator
- 1Measure the total length of all joints in feet.
- 2Measure the joint width and decide on the sealant depth.
- 3Choose square for gaps and triangular for inside-corner beads.
- 4Pick the tube size you will buy.
- 5Buy the number of tubes shown; keep one spare for touch-ups.
Formula and method
The cross-section of the joint is width × depth for a square joint, or half that for a triangular fillet bead. Multiplying by the length in inches (feet × 12) gives the sealant volume in cubic inches. A tube’s volume is its fluid-ounce size × 1.8047 cubic inches (one US fluid ounce is exactly 1.8046875 in³).
The calculator adds a waste allowance for the sealant left in the nozzle and tube and for tooling, then rounds up to whole tubes. Linear feet per tube is simply tube volume divided by the bead volume per foot.
- w, d
- Joint width and sealant depth (in)
- k
- 1 for square joints, 0.5 for triangular fillets
- L
- Total joint length (ft)
- oz
- Tube size in US fluid ounces
Worked examples
100 ft of 1/4 × 1/4 in joints, 10.1 oz tubes
0.25 × 0.25 × 1,200 in = 75 in³ of sealant, 82.5 in³ with 10% waste. A 10.1 oz tube holds 18.23 in³, so you need 4.5 tubes — buy 5. Each tube runs about 24 ft of this bead.
60 ft of 1/2 in wide expansion joint, 1/4 in deep
A 1/2 × 1/4 in section holds 0.125 in² × 720 in = 90 in³, or 99 in³ with waste. That is 5.4 cartridges, so buy 6; each runs about 12 ft.
40 ft of 3/8 in triangular bead around a tub
A triangular fillet is half of 0.375 × 0.375, or 0.0703 in². Over 480 in that is 33.75 in³ (37.1 in³ with waste), about 2.04 tubes, so buy 3.
Frequently asked questions
How many feet does a tube of caulk cover?+
A 10.1 oz cartridge holds about 18.2 cubic inches, which runs roughly 97 ft of a 1/8 × 1/8-inch bead, 24 ft of a 1/4 × 1/4-inch bead and about 6 ft of a 1/2 × 1/2-inch joint.
How deep should caulk be?+
Sealant manufacturers generally recommend a depth of about half the joint width for joints wider than 1/2 inch, with a minimum of around 1/4 inch, and equal to the width for narrow joints. Backer rod sets the depth.
What is backer rod and do I need it?+
Backer rod is a compressible foam cord pushed into deep joints before caulking. It controls sealant depth, saves material and prevents three-sided adhesion, which helps the joint stretch without tearing.
How much caulk is wasted?+
Some sealant always stays in the tube, nozzle and gun, and tooling removes a little more. A 10% allowance is typical; increase it if you are working overhead or on rough, uneven joints.
What size caulk tube should I buy?+
The 10.1 oz cartridge fits standard caulk guns and suits most household jobs. 20 oz sausage packs and 28 oz cartridges are cheaper per ounce on big siding or concrete jobs but need a larger gun.