Sealant Calculator
Caulk needed = joint length × bead width × bead depth ÷ cartridge volume — the calculator uses about 18.5 in³ per standard 10.1 oz tube. 100 ft of 3/8 × 3/8 in joint holds about 169 in³: 9.1 cartridges exact, 11 with 10% waste. With a backer rod, enter the depth above the rod.
How it's calculated: Cartridges = joint length × width × depth ÷ cartridge volume (10.1 oz ≈ 18.5 in³ as used here), plus waste.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Bead cross-section = joint width × joint depth
Sealant volume = joint length × bead cross-section
Cartridges = sealant volume ÷ cartridge volume (10.1 fl oz ≈ 18.5 in³)
Run the calculation to see each step with your own numbers.
100 ft of 3/8 in × 3/8 in joint, 10.1 oz cartridges, 10% waste.
Bead = 0.375 × 0.375 = 0.1406 in²
Volume = 1,200 in × 0.1406 = 168.75 in³
Cartridges = 168.75 ÷ 18.5 = 9.1 → order 11 with 10%
- A square/rectangular bead of the width and depth entered. A shallow surface bead over a wide joint uses much less than filling the full depth.
- A backer rod (recommended for joints over ~1/2 in wide) sets the depth — enter the depth above the rod, typically half the width.
- 10.1 fl oz cartridge ≈ 18.5 in³; a 29 oz cartridge ≈ 53 in³; a 20 oz sausage ≈ 37 in³.
- How many feet does one tube of caulk do?
- For a 1/4 in × 1/4 in bead, about 24 ft per 10.1 oz cartridge. For a 3/8 × 3/8 joint it drops to about 11 ft. The calculator works it out for your exact joint.
- What is a backer rod and when do I need one?
- A foam rope pushed into a joint wider than about 1/2 in before caulking. It sets the sealant depth, stops the bead bonding to the back of the joint so it can stretch, and saves sealant. Enter the depth above the rod, not the full joint depth.
- Standard cartridge or a bigger pack?
- A standard 10.1 fl oz cartridge holds about 18.5 in³. A 29 oz cartridge holds roughly three times that and a 20 oz sausage about twice — enter the size you're buying and the calculator adjusts the count.
- How many tubes of caulk do I need?
- Multiply the joint length by the bead width and depth for the volume, divide by the cartridge volume, and add about 10%. 100 ft of 3/8 × 3/8 in joint needs about 9 standard 10.1 oz tubes, or 11 with waste.
Geometry
Standard geometry (bead cross-section × length).
Cartridge volume
A 10.1 fl oz cartridge holds ≈ 18.5 in³ (≈ 300 mL) — sealant-manufacturer product data (e.g. Sika, DAP, Sikaflex).
About the Sealant Calculator
The Sealant Calculator works out how many cartridges of caulk or sealant a run of joint needs, from the joint length and the width and depth of the bead. A deeper or wider bead uses far more per foot — filling a 3/8-inch joint to full depth runs through a standard cartridge in about eleven feet. With a backer rod in a wide joint, enter the depth above the rod, which is usually about half the width.
What you enter
- Total joint length
- Joint width — The gap you're filling. A typical control joint is 3/8 in.
- Joint depth (bead) — How deep the sealant sits. With a backer rod, depth ≈ half the width for a wide joint.
- Cartridge size (fl oz) — Standard cartridge is 10.1 fl oz. Sausage packs and 29 oz cartridges hold more.
- Waste allowance — Covers priming the nozzle, tooling waste and a partly-used last tube.
What you get back
- Cartridges needed — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Coverage per cartridge — the exact result of the calculation.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
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