Tack Coat Calculator

Tack coat calculator formula

A tack coat calculator divides the area of pavement you are covering by the area one diluted gallon spreads over. Gallons = area ÷ 150. Cost = gallons × price per gallon, with $8 as the starting price. The tool does not round, so you see the exact number of gallons.

The formula in plain words

Multiply length by width to get the square feet. Divide by 150. The answer is the gallons of diluted emulsion for one pass. Because 150 sq ft per gallon is a general rate, change it if your supplier or the spec gives another.

Worked examples

These match the calculator exactly.

1. Short overlay strip: 40 ft × 12 ft, $8 per gallon

• Area: 480 sq ft
• Gallons: 480 ÷ 150 = 3.20
• Cost: 3.2 × $8 = $25.60

2. Longer road section: 200 ft × 12 ft

• Area: 2,400 sq ft
• Gallons: 2,400 ÷ 150 = 16.00
• Cost: 16 × $8 = $128

Tack coat is cheap next to asphalt itself. The cost lies in the time it takes to prepare the surface and apply it evenly.

Gallons by area

Area	Gallons at 150 sq ft per gallon
500 sq ft	3.33
1,000 sq ft	6.67
2,500 sq ft	16.67
5,000 sq ft	33.33
10,000 sq ft	66.67

Pavement specs are often written per square yard. 150 sq ft per gallon is 150 ÷ 9 = 16.67 sq yd per gallon, which is about 0.06 gallons per square yard. Compare that with the figure in your spec.

When tack coat is used

Tack coat is sprayed between asphalt lifts, on old pavement before an overlay, and on vertical edges such as curbs and utility covers before new asphalt meets them. The surface should be clean and dry. Sweep away dirt and loose material, since emulsion that sticks to dust does not bond to the pavement. Let the emulsion break, which means it turns from brown to black as the water leaves, before paving over it.

Applying it

A distributor truck sprays large jobs, and a hand wand is used on small ones. The goal is a thin, even film with no puddles. Too much can make the new layer slip, and too little may not bond. Keep traffic off the coat, since tires pick it up. Avoid applying it when rain is expected, or in cold weather outside the product’s range.

How to measure

Measure the length and width of each section being overlaid and multiply. For a road with curves, take several widths and use the average. Add the edges that will be tacked, like curb faces, as extra area. For parking lots, split the lot into rectangles and add up the totals.

What to buy

Emulsion is sold by the drum, the tote and the pail, and the price depends on the product and how it is delivered. Many small jobs use a few pails. Check how the supplier gives the volume, since some quote the undiluted product and some quote the diluted mix. If you buy undiluted emulsion and dilute it yourself, a 1 to 1 mix doubles the volume, so 3.2 diluted gallons needs about 1.6 gallons of undiluted product. The right ratio is on the label.

Buy a little more than the tool says. Spray patterns overlap, hoses hold some liquid, and edges take more than the flat area suggests.

Edges and joints

Vertical faces such as curbs, gutters and the edge of an existing mat need tack coat too, because the new asphalt meets them. They are small in area but easy to miss. Measure the edge length and the height and add that area to the flat area. A 40 ft edge that is 0.5 ft high adds 20 sq ft, or 0.13 gallons at 150 sq ft per gallon.

Common mistakes

• Using the diluted rate with an undiluted product.
• Applying over dust or standing water.
• Paving before the emulsion breaks.
• Applying too thick.
• Skipping the extra for overlap and edges.

Related pages

To size the new layer, see the asphalt overlay calculator and the asphalt calculator. For protecting finished pavement, see the sealcoat calculator.