A standard 10.1 fl oz cartridge of caulk runs about 31 linear feet with a 1/4 in round bead and 55 ft with a 3/16 in bead, which is the figure DAP prints on its data sheets. So 40 ft of joints at 1/4 in takes 2 cartridges once you allow 10% for tooling and what stays in the tube. Bead size matters more than anything else: doubling the bead to 1/2 in cuts the coverage to about 7.7 ft per tube.
How caulk coverage is calculated
A tube holds a fixed volume, and the bead is a long thin prism, so the length one tube covers is its volume divided by the bead's cross-section. One US fluid ounce is 1.805 cubic inches, so a 10.1 fl oz cartridge holds 18.2 cu in.
feet per tube = tube volume (cu in) ÷ bead cross-section (sq in) ÷ 12
The cross-section depends on the shape of the bead:
- Round bead over a gap: π × diameter² ÷ 4.
- Corner fillet in an inside corner (tub to tile, counter to backsplash): a triangle with equal legs, leg² ÷ 2.
- Wide joint over backer rod: width × sealant depth.
This geometry is exactly what the manufacturers use: DAP rates both ALEX PLUS and ALEX ULTRA at 55 linear ft per 10.1 fl oz at a 3/16 in bead and 30 ft per 5.5 fl oz, and the formula gives 55.0 and 30.0 ft.
Worked example: 40 ft at a 1/4 in bead
The calculator opens on 40 ft of joint, a 1/4 in round bead and 10.1 fl oz cartridges:
- Cross-section: π × 0.25² ÷ 4 = 0.0491 sq in.
- One cartridge: 18.23 cu in ÷ 0.0491 sq in ÷ 12 = 30.9 ft.
- Tubes: 40 ft × 1.10 ÷ 30.9 ft = 1.42, so 2 tubes.
The same 40 ft as a 1/4 in fillet in a corner takes only half the caulk of a square joint: 48.6 ft per cartridge, 1 tube.
Linear feet per 10.1 oz tube by bead size
| Bead size | Round bead | Corner fillet |
|---|---|---|
| 1/8 in | 123.8 ft | 194.4 ft |
| 3/16 in | 55.0 ft | 86.4 ft |
| 1/4 in | 30.9 ft | 48.6 ft |
| 3/8 in | 13.8 ft | 21.6 ft |
| 1/2 in | 7.7 ft | 12.2 ft |
No waste is included in the table. Sashco rates a 10.5 oz cartridge of Big Stretch at about 26 ft with a 1/4 in bead, lower than the 32 ft the geometry gives, because a real bead is rarely a perfect circle and some caulk is tooled off. That gap is why the calculator adds 10% by default; raise it to 20% if you tool hard or your beads run fat.
How many tubes of caulk for windows and doors
Pick Windows, doors and enter how many and their size. Each window is sealed around its full perimeter, 2 × (width + height). Six 3 × 4 ft windows are 6 × 14 ft = 84 ft of joint: at a 1/4 in bead that is 3 tubes for one side, 6 if you also seal inside. Exterior trim and siding gaps are often wider than 1/4 in; measure a few gaps before you pick the bead size.
Caulk for a bathtub or shower
For an alcove tub, Tub or shower adds the joint along the back wall, both end walls and the two inside corners up the wall. A 60 × 30 in tub with 72 in corners is 60 + 2 × 30 + 2 × 72 = 264 in, or 22 ft: 1 tube at 1/4 in, with some left for the faucet and drain. Use a 100% silicone or a sealant labeled for tubs and showers there.
Wide joints and backer rod
Wide joints, such as concrete control joints or gaps around exterior doors, are usually filled over closed-cell backer rod so the sealant is a thin band that can stretch. Pick Wide joint and enter the width and the sealant depth; the depth comes from your sealant's data sheet. A 1/2 in wide joint filled 1/4 in deep uses 0.125 sq in per foot, 12.2 ft per 10.1 oz cartridge. The material list adds backer rod for the length of the joint.
5.5, 10.1 or 20 oz tubes
A 5.5 fl oz squeeze tube is for a single small job. The 10.1 fl oz cartridge fits a standard caulk gun and is what most coverage figures refer to. A 20 fl oz cartridge or sausage pack holds almost twice as much, 61 ft of 1/4 in bead, but needs a larger gun.
What to work out next
- The countertop and backsplash you are sealing: the countertop calculator.
- Tile for the backsplash: the backsplash tile calculator.
- Tile and grout for a tub surround: the shower tile calculator and the grout calculator.
- Trim that will be caulked and painted: the trim calculator.
- All floor, tile and sealant tools: floors, tile and countertop calculators.