Calculate how many tubes of sealant you need to fill a joint of a given size.
Usage Tip
Use a backer rod in deep joints so the sealant bonds to just two sides and can flex without tearing.
fluid ounces = cu in × 0.554
tubes = round up( fluid ounces ÷ 10.1 )
A standard tube holds about 10.1 fluid ounces.
How Much Sealant Do I Need?
Measure the joint width and depth and the total linear feet. Multiply width by depth by length for the volume, then divide by the cartridge volume. A standard 10 oz cartridge holds about 18 cubic inches and seals roughly 24 ft of a 1/4 x 1/4 in joint.
Sealant Coverage Chart
Approximate linear feet from one 10 oz cartridge (about 18 cu in):
| Joint (W x D) | Coverage per 10 oz |
|---|---|
| 1/4 x 1/4 in | about 24 ft |
| 1/4 x 3/8 in | about 16 ft |
| 3/8 x 3/8 in | about 11 ft |
| 1/2 x 1/4 in | about 12 ft |
| 1/2 x 3/8 in | about 8 ft |
| 1/2 x 1/2 in | about 6 ft |
Sealant Types
| Type | Best for |
|---|---|
| Silicone | Bath, kitchen, glass, metal; waterproof, not paintable |
| Polyurethane | Exterior, movement joints, concrete; paintable, durable |
| Acrylic latex | Interior trim and gaps; paintable, easy cleanup |
| Construction | Structural gaps and bonding; high strength |
| Concrete / self-leveling | Horizontal concrete and expansion joints |
Backer Rod Sizing
For deep or wide joints, push in a closed-cell backer rod first. It controls depth (aim for a sealant depth of about half the width), saves sealant, and lets the bead flex. Pick a rod about 25% larger than the joint so it stays put:
| Joint width | Backer rod diameter |
|---|---|
| 1/4 in | 3/8 in |
| 1/2 in | 5/8 in |
| 3/4 in | 7/8 in |
| 1 in | 1-1/4 in |
Movement Joint Guide
Movement (working) joints flex with temperature and load, so the sealant must stretch. The classic rule is a width-to-depth ratio of 2:1 on wide joints (depth about half the width, 1/4 in minimum), with backer rod setting the depth and preventing three-sided adhesion. Three-sided adhesion (bonding to the backer too) tears the bead – the rod or a bond-breaker tape prevents it.
Concrete Expansion Joint Guide
Concrete slabs need expansion and control joints sealed against water and debris. Use a self-leveling polyurethane or concrete sealant for horizontal joints; tool vertical joints with a non-sag product. Clean the joint, install backer rod to the right depth, then fill. Sidewalk and driveway joints are commonly 1/4 to 1/2 in wide.
Exterior Window & Door Sealing
Seal the perimeter gap between the frame and the wall with a paintable polyurethane or high-grade siliconized acrylic. Leave weep holes clear at the bottom of windows. A typical window perimeter is 17-20 ft; a door is about 17 ft.
Bathroom & Kitchen Sealing
Use a mildew-resistant 100% silicone around tubs, showers, sinks, and countertops – it is waterproof and stays flexible. Fill the tub with water before sealing the base so the joint is at its widest, and tool a clean concave bead.
Cure Time Guide
| Type | Skin / tack-free | Full cure |
|---|---|---|
| Silicone | 15-30 min | 24 hours |
| Polyurethane | 1-2 hours | 3-7 days |
| Acrylic latex | 30 min | 1-2 weeks to fully cure/paint |
Temperature & Surface Prep
Apply most sealants between about 40 and 100 F on a clean, dry, sound surface. Remove old sealant, dust, and grease; for silicone, surfaces must be free of soap film. Mask both sides, gun the bead, tool it, then pull the tape before it skins.
Paintable vs Non-Paintable & Compatibility
Frequently Asked Questions
How many tubes of sealant do I need?
Depends on joint size: one 10 oz cartridge covers about 24 ft of a 1/4 in joint but only 6 ft of a 1/2 in square joint. Enter your joint and run above.
Do I need backer rod?
Yes for joints deeper than about 1/2 in or wider than 1/4 in – it sets depth, saves sealant, and lets the joint move.
Silicone or polyurethane?
Silicone for wet, non-painted areas (bath, glass); polyurethane for exterior, concrete, and anywhere you will paint.
Can I paint over sealant?
Over polyurethane and paintable acrylics, yes. Not over pure silicone.
What size cartridge is standard?
10 to 10.1 oz is the common caulk-gun cartridge; 29 oz quad tubes and 20 oz sausage packs cover big jobs.
How long before it gets wet?
Silicone is typically water-ready in about 24 hours; polyurethane takes several days to fully cure.
Related Calculators
Note: coverage and cure figures are approximations and vary by product, joint profile, temperature, and tooling. Always follow the manufacturer label for ratios, backer rod use, paintability, and compatibility, and buy a little extra. General DIY guidance, not a professional specification.