Bitumen emulsion needed for a tack coat before the next bituminous layer.
Bitumen Tack Coat Calculator: Free Online Tool
A tack coat is a thin film of bitumen emulsion sprayed on an existing surface before a new bituminous layer is laid on it. It makes the two layers bond so that they act together and do not slip or peel under traffic. Spraying the correct amount is important, because too little gives poor bond and too much can make the new layer unstable.
This calculator finds the sprayed area from length and width and multiplies it by the rate of spread for the surface you choose. It gives the bitumen required in kg, tonnes and litres, and includes wastage. Site engineers, contractors and estimators use it to order material and to check consumption against the area completed. The tool works in feet and inches or in metres and millimetres, so it suits both older site practice and metric drawings, and every result can be rechecked by hand.
When to use this calculator
Use it before laying a bituminous layer such as DBM or bituminous concrete over a primed granular surface or over an existing bituminous surface. It helps you prepare an estimate, order emulsion for a day's work, or check how much was actually used. You can enter the dimensions in feet or metres. There is a selector for the type of surface and a custom option if your specification gives a different rate. Adjust wastage to suit site conditions. It also gives a quick check on quotations and site requests before work starts.
How to use the Bitumen Tack Coat Calculator
- Open the calculator above on your phone, tablet or computer. Nothing needs to be installed and no sign-up is required.
- Choose the unit system first (feet / inches or metres / mm). The input labels change to match your choice.
- Pick the option you need from the drop-down list (Granular surface treated with primer (0.25 kg/m²); Existing bituminous surface (0.20 kg/m²); Custom rate).
- Enter your values in the input boxes: Length (ft), Width (ft), Surface to be tacked, Rate of spread (kg per m²), Density of binder (kg per litre), Wastage (%). The boxes already hold sample values, so overwrite them with your own.
- Press Calculate. The result appears straight away under the button.
- Change any value and press Calculate again to compare options. Press Reset to go back to the sample values.
- Check the result against your drawings, project specification and local code before you order material or approve work.
How the calculation works
The calculator uses Quantity = area x rate of spread. Area is length x width, converted to square metres if you enter feet. The surface selector sets the rate: 0.25 kg per m2 for a granular surface treated with primer, 0.20 kg per m2 for an existing bituminous surface, or a custom value. The note describes these as typical rates for RS-1 bitumen emulsion. Mass is divided by the binder density, 1.0 kg per litre by default, to give litres, and wastage is added. For 1,000 ft x 24 ft (2,229.67 m2) at 0.25 kg per m2, the result is 557.4 kg, 0.557 tonnes and 557 litres.
Worked example
When you open the page the calculator is filled with sample values. Pressing Calculate with those values gives the result below, which you can use to check that you are reading the output correctly.
| Area | |
|---|---|
| Area to be sprayed | 24,000.00 sq ft (2,229.67 m²) |
| Bitumen required | |
| Quantity (kg) | 557.4 |
| Quantity (tonnes) | 0.557 |
| Quantity (litres) | 557 |
Tips and common mistakes
- Pick the surface type that matches the actual base. A primed granular surface and an existing bituminous surface use different default rates.
- Use the custom rate if your project specification or the supplier recommends a value other than the defaults of 0.25 and 0.20 kg per m2.
- Check the unit system before entering length and width. Feet and metres give very different areas, so confirm the area shown in the result.
- Clean the surface of dust and loose material before spraying, and spray evenly. A correct quantity does not help if the distribution is patchy.
- Check the binder density on the supplier data sheet. The default of 1.0 kg per litre is approximate and affects the litre figure.
Frequently asked questions
What rates does the calculator use for tack coat?
The defaults are 0.25 kg per m2 for a granular surface treated with primer and 0.20 kg per m2 for an existing bituminous surface. These are typical values for RS-1 emulsion. Use your specification if it differs.
How do I use a different rate?
Choose the custom rate option in the surface selector and enter your own rate in kg per m2. This is useful when the specification or supplier gives a specific value for your project.
Does the result include wastage?
Wastage is a percentage you enter, and the default is 0. If you enter a value, it is added to the theoretical quantity. Include an allowance to cover losses at the start and end of spraying.
Why does the calculator show litres as well as kg?
Many suppliers and sprayers measure emulsion by volume. The calculator divides the mass by the binder density, 1.0 kg per litre by default, to give litres. Change the density if your data sheet differs.
Can I use it for a prime coat?
The formula is the same, but prime coat rates are higher and apply to a granular base. A separate prime coat calculator is available with a typical rate of 0.70 kg per m2.
Important note
This tool gives estimates for planning, study and quick checks. It does not replace design by a qualified engineer, site-specific testing, or the requirements of your project specification and local building code. Always confirm final quantities, test results and acceptance limits with the responsible engineer before using them for construction or payment.
