Enter the crack dimensions and select your repair product to instantly calculate how much filler, caulk, or epoxy you need — with tube/cartridge counts and an optional cost estimate.
Free to use
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Covers all common repair products
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Imperial & metric supported
✓ Tube & cartridge counts✓ 4 repair product types✓ Overage factor built in✓ Last verified May 2026
Select the product you plan to use. Yields are based on manufacturer data sheets.
Measure the full run of the crack with a tape measure. Add all sections together.Please enter a valid crack length greater than 0.
Measure the widest point and the narrowest, then average them. Use a feeler gauge for accuracy.Please enter a valid crack width greater than 0.
For surface cracks, probe with a wire or feeler gauge. If depth is unknown, use 1.5× the width as an estimate.Please enter a valid crack depth greater than 0.
15% is recommended — crack profiles are irregular and products cure with slight shrinkage.
$
Cost per tube/cartridge/bag. Leave blank to skip cost estimate. Typical range: $8–$35 per unit depending on product.
Results appear instantly. No sign-up required.
Your Crack Repair Estimate
Crack Volume (with overage)
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Cubic Inches (in³)
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Fluid Ounces (fl oz)
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Milliliters (mL)
Units Required
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Minimum units
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Recommended (incl. overage)
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Product type selected
—Net Volume (in³)
—Crack Area (in²)
—Overage Factor
—Yield per Unit (in³)
Estimated Material Cost
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Repair material cost only. Does not include tools, backer rod, surface prep products, or labor. Use our Full Project Estimator for a complete breakdown.
Step 1: Convert all inputs to inches
Step 2: Net Volume (in³) = Length (in) × Width (in) × Depth (in)
Step 3: Adjusted Volume = Net Volume × (1 + overage% ÷ 100)
Step 4: Units Required = CEIL(Adjusted Volume ÷ Yield per Unit)
Note: Crack volume is treated as a rectangular prism. Real cracks taper — the 15% overage accounts for irregular cross-sections.
How to Use This Concrete Crack Repair Calculator
Select your repair product type.
The product selection drives everything — each material has a different yield, application method, and best-use scenario. If you haven't bought product yet, pick the type that matches your crack profile (see the crack type guide below). Polyurethane caulk is the go-to for non-structural cracks in flatwork; epoxy injection is for structural cracks in walls, beams, or foundations that need bonding strength.
Measure and enter your crack dimensions.
Use a tape measure for length, a feeler gauge or credit card for width, and a stiff wire probe for depth. If the crack varies significantly in width, average at least 3 measurements across its length. Enter total crack length — if you have multiple cracks, add their lengths together. Use the unit dropdowns to match whatever units you're measuring in.
Keep the 15% overage factor.
Real cracks are never perfect rectangles — they taper, widen in places, and change direction. Products also lose a small amount to mixing, priming the nozzle, and trimming the tip. The default 15% accounts for this. For particularly irregular or branching cracks, increase it to 20–25%.
Use the results to buy exactly what you need.
The calculator tells you the minimum and recommended unit counts. Buy the recommended quantity — having a partial tube left over costs you a few dollars; running out mid-repair means the fresh material you've already applied starts to skin over before the next tube arrives, and the bond between the two applications will be weaker than a single continuous fill.
⚠ Pro Tip: For cracks wider than ¾ inch, install closed-cell polyethylene backer rod first. Backer rod reduces the volume of filler needed (sometimes by 60–70%), prevents three-sided adhesion (which causes premature failure), and gives you a consistent fill depth. Never fill a wide crack with sealant from the bottom up without backer rod — the cured bead will be too thick, too stiff, and will crack again within a season.
Crack Repair Material Volume Formula
The calculation models the crack as a rectangular prism and divides the total adjusted volume by the per-unit yield of the selected product. Here is the step-by-step process with a worked example:
Values rounded up to whole units. Add 15% overage already included. Backer rod use can dramatically reduce quantities for wide cracks — install backer rod at ½–¾ inch below surface for cracks wider than ½ inch.
Which Repair Product Should I Use?
Product selection is the most critical decision in crack repair. Using the wrong product for your crack type results in premature failure, regardless of how well you apply it. The table below covers the most common crack scenarios in residential and commercial concrete.
Recommended repair product by crack type, location, and structural role.
Crack Type
Width Range
Best Product
Notes
Hairline surface crack (driveway, patio)
< 1/16 in
Concrete sealer / penetrating silane
Too narrow for caulk; seal to prevent water infiltration
Working crack in flatwork (seasonal movement)
1/16–½ in
Polyurethane / polyurea caulk
Flexible sealant tolerates expansion and contraction — do not use epoxy
Non-moving crack in slab or driveway
¼–¾ in
Routing compound or PU caulk
Route to uniform ¼ in width × ½ in depth for best sealant bed
Structural crack in wall, beam, or foundation
Any width
Epoxy injection
Bonds crack monolithically; resists tension loads — requires professional equipment for deep cracks
Active water leak (basement wall, dam)
Any width
Hydraulic cement
Sets under flowing water in 3–5 minutes; permanent patch, not flexible
Wide void or spalled section
> ¾ in
Sand-mix mortar + bonding agent
Use backer rod for deeper voids; hydraulic cement for wet conditions
Expansion joint failure
¼–1 in
Self-leveling polyurethane caulk
Remove old sealant completely; install backer rod before applying
Never use rigid epoxy in a crack that undergoes seasonal thermal movement. As the concrete expands and contracts, it will shear right through the epoxy bond and crack again — often wider than before. Epoxy is for structural repairs only, where the goal is to restore tensile strength, not accommodate movement.
Common Mistakes When Repairing Concrete Cracks
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Skipping surface preparation.
Crack filler bonds to clean, dry, dust-free concrete — not to dirt, oil, old sealant, or laitance. Blow out the crack with compressed air, remove any loose material with a wire brush or angle grinder, and let it dry completely before applying any product. Applying filler to a contaminated surface is the single most common reason crack repairs fail within one season.
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Filling a wide crack without backer rod.
Polyurethane and polyurea sealants are designed to work with a specific fill depth relative to crack width — typically a 1:1 or 2:1 depth-to-width ratio. Without backer rod, you fill the full depth, the sealant becomes too thick to flex, and it splits in the middle under thermal stress. For cracks wider than ½ inch, backer rod is non-negotiable.
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Using flexible caulk on a structural crack.
A crack that has compromised the structural integrity of a wall, beam, or foundation needs epoxy injection — not sealant. Flexible caulk does nothing to restore tensile strength. If a structural crack is not properly bonded, the element continues to deflect under load, and the crack propagates further. When in doubt about structural implications, consult an engineer before doing anything.
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Repairing an active water-leaking crack with standard products.
Epoxy will not bond to a wet surface, and most polyurethane sealants require dry conditions. If water is actively entering through a crack, the correct product is hydraulic cement — it generates heat during hydration and sets under flowing water. Apply it by plugging the crack from the outside in, using gloved hands to hold pressure for 3–5 minutes until it reaches initial set.
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Underestimating material quantity and running out mid-repair.
Fresh sealant or epoxy that skins over before you can complete the joint creates a bond plane within the repair — exactly the kind of weak point you're trying to eliminate. Always buy the recommended quantity (minimum plus overage) before you start. A partial tube of leftover sealant costs a few dollars; a failed repair that needs to be removed and redone costs far more.
Frequently Asked Questions
Multiply the crack's length by its width by its depth — all in the same unit (inches is most practical) — to get the volume in cubic inches. Add 15% for overage. Then divide by the yield of your selected product (e.g. 18.6 in³ for a standard 10.1 fl oz polyurethane caulk tube) and round up to whole units. This calculator does all of that automatically. For example, a 36-inch crack that is ¼ inch wide and 2 inches deep has a net volume of 18 in³ — requiring 2 tubes of polyurethane caulk with 15% overage.
For cracks in driveways and flatwork, polyurethane or polyurea sealant is the correct choice for cracks between 1/16 inch and ½ inch wide. These products are flexible — they expand and contract with seasonal temperature swings without debonding. For wider cracks, install backer rod first and use a self-leveling polyurethane caulk. Avoid epoxy on driveways because driveways are subject to thermal movement, and a rigid epoxy bond will fail under that stress. For very narrow hairline cracks, a concrete penetrating sealer is more effective than caulk.
Backer rod is closed-cell polyethylene foam rope that you press into a crack before applying sealant. Its purpose is twofold: it controls the depth of the sealant to the correct fill profile (typically 1:1 or 2:1 depth-to-width), and it prevents "three-sided adhesion" — where the sealant bonds to the bottom of the crack as well as both walls. Three-sided adhesion prevents the sealant from stretching freely when the crack moves, causing it to tear. For any crack wider than ½ inch, backer rod is essential and will reduce material consumption significantly. Install backer rod ½ to ¾ inch below the surface.
Use epoxy injection when the crack is structural — meaning it has compromised the member's ability to carry tension loads — or when you need to restore the concrete to a monolithic condition. Typical applications include cracks in foundation walls, basement walls, concrete beams, columns, and parking structure decks where water infiltration and structural continuity are both concerns. Epoxy is not appropriate for cracks that undergo seasonal movement: as the concrete expands and contracts, the rigid epoxy bond shears. A simple rule: if the crack moves, use flexible sealant. If the crack is dormant and in a load-bearing member, use epoxy.
For cracks in flatwork, push a stiff wire (a coat hanger works) straight down into the crack until it stops and mark the surface entry point with your thumb. Pull it out and measure. For cracks in walls, use the same wire-probe method. If the crack appears to go all the way through the element (e.g. a through crack in a basement wall), assume depth equals wall thickness. When you can't determine depth with confidence, a conservative estimate of 1.5 times the surface width is reasonable for most flatwork cracks — and the 15% overage in this calculator provides additional buffer.
Most polyurethane sealants require the substrate to be dry and above 40°F for proper curing and adhesion. Applying sealant to a frozen or wet crack results in poor bond and premature failure — the moisture gets trapped between the sealant and concrete wall. Epoxy injection requires even stricter conditions — typically above 50°F and completely dry. The one exception is hydraulic cement, which is specifically designed to cure in wet conditions and even under flowing water. If you have an active water intrusion emergency in winter, hydraulic cement is your only field-viable option.
Routing makes a significant difference in repair longevity. A natural crack has irregular, tapered walls that provide inconsistent bonding surfaces. Routing creates a uniform rectangular channel — typically ¼ inch wide by ½ inch deep — that gives the sealant consistent depth, a flat bonding wall, and a clean substrate with freshly exposed aggregate. ASTM C780 and most state DOT specifications require routing before sealing on pavement and bridge deck cracks. For homeowner repairs, routing is optional but strongly recommended for cracks that are either very narrow or very irregular in cross-section.
With correct product selection, surface preparation, and application technique, polyurethane sealant repairs on flatwork typically last 5–10 years before needing reapplication. Epoxy injection repairs on dormant structural cracks can last the life of the structure. Hydraulic cement patches on leaking walls are permanent repairs in many cases. The most common reason crack repairs fail early is poor surface prep — specifically contaminated or wet substrates, or applying a rigid product to a moving crack. Investing an extra 20 minutes in preparation extends repair life dramatically.
There is no absolute maximum width for sealant repairs, but once a crack exceeds about 1 inch wide, a simple caulk or routing seal is usually not the right approach. Cracks that wide typically indicate significant structural movement, differential settlement, or expansive soil pressure — problems that sealant alone cannot address. Cracks over 1 inch in flatwork are usually better handled by removing and repouring the damaged section, or installing a proper saw-cut expansion joint. For wall cracks over 1 inch, consult a structural engineer before attempting any repair — the crack may be symptomatic of a larger foundation issue.
Most modern polyurethane and polyurea caulks are self-priming when applied to clean, dry concrete and do not require a separate primer. However, for epoxy injection into porous or contaminated substrates, a low-viscosity primer or flush is often recommended by the manufacturer to open the pores and improve penetration. Always check the product's data sheet. On high-absorption substrates (older, worn concrete) or for critical structural applications, priming noticeably improves bond strength. Hydraulic cement does not require primer — the hydraulic pressure and heat from the reaction provide the bond.
