Tack Coat Calculator
Calculate gallons of tack coat emulsion needed to bond an asphalt overlay to the existing surface, plus total material cost.
How this calculator works
Tack coat is sprayed at a set coverage rate onto an existing asphalt surface before an overlay lift is paved. This calculator divides your surface area by the standard 150 square feet per gallon coverage rate for diluted emulsion to get the gallons needed.
Formula: Gallons = Surface area (sq ft) ÷ 150 sq ft per gallon.
Worked example
A 40 ft × 12 ft overlay section (480 sq ft):
- Gallons: 480 ÷ 150 = 3.20 gallons
- At $8/gallon, that’s $25.60.
Coverage reference
| Surface area | Gallons needed |
|---|---|
| 20 ft × 6 ft | 0.80 gallons |
| 40 ft × 12 ft | 3.20 gallons |
| 80 ft × 24 ft | 12.80 gallons |
How to measure your surface
Measure the full existing surface area that will receive the new overlay lift, in feet, the same footprint you’d use for the overlay tonnage calculation itself. Tack coat only needs to cover the area being overlaid — don’t include adjoining surfaces that aren’t being resurfaced.
Frequently asked questions
What is tack coat and why is it needed?
Tack coat is a thin, diluted asphalt emulsion sprayed onto an existing surface before a new overlay lift is placed. It bonds the new asphalt to the old layer beneath it — without it, the overlay can slip, shove, or delaminate under traffic since the two lifts never fuse into one structural section.
How much coverage does one gallon of diluted tack coat provide?
About 150 square feet per gallon at typical application rates for a diluted emulsion. Application rate varies by emulsion type and surface porosity, so this is a planning estimate — your paving crew's spray equipment is usually calibrated to a specific rate for the product being used.
Is tack coat the same thing as sealcoat?
No — tack coat is a bonding layer sprayed between two asphalt lifts during construction, applied thin and covered almost immediately by the new pavement. Sealcoat is a protective, weather-resistant topcoat applied to a finished, exposed driveway surface and left to cure in the open. They use different products and serve entirely different purposes.
When in the overlay process does tack coat get applied?
After crack sealing and pothole patching, but before the new overlay lift is paved — it's the last prep step on the existing surface. Applying it too early lets dust and debris settle on the tacky surface, which weakens the bond before the overlay ever goes down.
Why isn't waste added to the tack coat calculation?
Tack coat is sprayed as a liquid at a controlled application rate rather than cut from sheet stock, so there's no cutting waste to account for. Any leftover emulsion in the tank is simply used on the next section or job rather than discarded.
Estimates only. Verify quantities with your supplier before purchasing.