How it works
The calculator works out the cross-section of the bead or joint, divides the cartridge volume by it to get the length one cartridge fills, and divides the joint length by that length.
Round bead: Cross-section = π × Diameter² ÷ 4
Joint: Cross-section = Width × Depth
Length per cartridge = Cartridge volume ÷ Cross-section
Cartridges = ⌈ Joint length × (1 + Extra ÷ 100) ÷ Length per cartridge ⌉
Sealant = Joint length × (1 + Extra ÷ 100) × Cross-section
⌈ ⌉ means rounding up to whole cartridges. When you pick a line from a yield table, the length per cartridge comes from the table instead, and the sealant volume is the number of cartridges’ worth times 10.1 fl oz.
Worked example in words
A 3/16 in round bead has a cross-section of π × (3/16)² ÷ 4 = 0.0276 square inches. A 10.1 fl oz cartridge holds 10.1 × 231 ÷ 128 = 18.23 cubic inches (one US gallon is 231 cubic inches and 128 fluid ounces, NIST Handbook 44), so it fills 18.23 ÷ 0.0276 = 660 in, or 55 ft – the same 55 ft DAP prints on its data sheet for that bead. For 100 ft of joint that is 100 ÷ 55 = 1.82, so two cartridges.
Bead size matters more than anything
The volume of a bead grows with the square of its size. Going from a 3/16 in to a 1/4 in round bead takes almost 80 % more caulk per foot, and a 1/2 × 1/2 in joint takes about nine times as much as a 3/16 in bead. That is why a cartridge can run 55 ft on fine trim work and only about 6 ft in a wide expansion joint. Measure the gap you are filling, not just the nozzle you cut.
Yield tables from sealant makers
Sika’s data sheet for Sikaflex Construction Sealant gives a yield table for a 300 mL (10.1 oz) cartridge by joint width and depth, from 24.2 ft (7.4 m) at 1/4 × 1/4 in to 3.0 ft (0.9 m) at 1 × 1/2 in. Those figures match the width × depth calculation for the nominal inch sizes, and they are offered as table lines. Sika also says the sealant is used no deeper than 13 mm (1/2 in) with closed-cell backer rod, and DAP says its ALEX PLUS joints should not exceed 1/2 in wide by 1/2 in deep, with backer rod for deeper joints. Other products have their own limits – check the data sheet for the sealant you use.
In metric, enter the bead in millimetres and the cartridge in millilitres; 300 mL is filled in because both data sheets list that size. A 6 mm round bead from a 300 mL cartridge runs about 10.6 m.
Worked example
Inputs
- Total joint length
- 100 ft
- Bead or joint
- Round bead (diameter)
- Bead diameter
- 3/16 in
- Cartridge size
- 10.1 fl oz
- Extra
- 0 %
Result
- Length per cartridge
- 55.01 ft
- Sealant volume
- 18.36 fl oz (0.143 gal)
- Cartridges
- 2
Common mistakes
- Measuring only one side of a window or door. A window has four sides to caulk, and inside and outside are separate joints.
- Using the nozzle hole as the bead size. The bead is usually a little larger than the cut, and a filled joint is the full width of the gap.
- Filling a deep gap with caulk alone. Deep joints waste sealant and can fail; data sheets call for backer rod when the joint gets deeper than they allow.
- Assuming every cartridge is the same size. Squeeze tubes, standard cartridges and sausage packs hold very different amounts – use the volume on the label.
- Expecting the label coverage on a wider bead. A 3/16 in bead runs about 55 ft per 10.1 fl oz cartridge, but a 1/4 × 1/4 in joint only about 24 ft.
Assumptions and limits
- A round bead has the cross-section of a circle of the diameter you enter; a joint is filled to a rectangle of width × depth.
- The whole cartridge volume goes into the joint. Extra for the nozzle, the cartridge end and tooling is added only through the extra field.
- Table lines use the maker’s published length per 10.1 fl oz (300 mL) cartridge for that joint size; the sealant volume is worked out from it.
- Cartridges are rounded up to whole cartridges. Partly used cartridges from earlier jobs are not counted.
- The calculator does not choose a sealant or check movement capability, joint design or backer rod size – follow the product’s data sheet.
Frequently asked questions
How many feet does a tube of caulk cover?
It depends on the bead. DAP’s data sheet says a 10.1 fl oz cartridge of ALEX PLUS covers 55 linear feet at a 3/16 in bead. A 1/4 × 1/4 in joint takes about 24 ft per cartridge and a 1/2 × 1/2 in joint about 6 ft, per Sika’s yield table.
How much caulk do I need for a bathtub?
Measure the joint around the tub – typically the back wall plus both ends – and enter it with the bead size you plan. A 5 ft tub with 30 in ends is 5 + 2.5 + 2.5 = 10 ft of joint; at 55 ft per cartridge with a 3/16 in bead, one cartridge is plenty.
How do I work out caulk from joint width and depth?
Multiply width by depth to get the cross-section, then divide the cartridge volume by it. A 10.1 fl oz cartridge holds 18.23 cubic inches (one US gallon is 231 cubic inches); a 1/4 × 1/4 in joint is 0.0625 square inches, so one cartridge fills 18.23 ÷ 0.0625 = 292 in, or about 24 ft.
What size cartridge should I enter?
The volume on the label. DAP and Sika both list 10.1 fl oz (300 mL) cartridges, which is the default here; small squeeze tubes and 20 fl oz or 600 mL sausage packs are entered with their own volume.
Should I buy extra caulk?
Usually yes. Sealant stays in the nozzle and the cartridge, gaps are rarely even, and tooling removes some. Add a small extra percentage or buy one more cartridge than the result.
Sources
- ALEX PLUS Acrylic Latex Caulk Plus Silicone (White) – Technical Data Sheet (5/12/25) — DAP. 10.1 fl oz (300 mL) cartridge: 55 linear feet at a 3/16 in diameter bead; joints up to 1/2 in wide × 1/2 in deep, backer rod when deeper.
- Sikaflex Construction Sealant – Product Data Sheet — Sika Canada. 300 mL (10.1 oz) cartridge yield by joint width × depth, from 7.4 m (24.2 ft) at 6 × 6 mm (1/4 × 1/4 in) to 0.9 m (3.0 ft) at 25.4 × 13 mm (1 × 1/2 in); sealant depth up to 13 mm (1/2 in).
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 4, 2026