Tar and Gravel Roof Cost Calculator: Estimate Costs

Last updated: 06 Oct 2026 | Author: Brij | Review By: Irshad

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Use the Tar and Gravel Roof Cost Calculator to estimate the budget for installing or replacing a built-up roof. Enter the roof area, material costs, labor costs, and any additional expenses to get a clear preliminary cost estimate.

Enter roof dimensions

Roof length:

Roof width:

Roof area:

Enter Tar Coverage and cost

Tar Coverage (gallons per square unit):

Tar Cost:

per gallons

Tar need

gallons

Total Tar Cost:

Enter Gravel Coverage and cost

Gravel Coverage (pounds per square unit):

Gravel Cost:

per pounds

Gravel need:

pounds

Total Gravel Cost:

Enter Labor and Additional costs

Labor Cost (per square unit):

Total Labor Cost

Result

Total Cost (Tor + Gravel + Labor Cost:):

What is Tar and Gravel?

Tar and Gravel is a type of roofing system that consists of layers of asphalt (tar) and roofing felt, topped with a layer of gravel or stone. It is commonly used for flat or low-slope roofs, with the gravel providing protection against UV rays and weather damage while adding weight to keep the roofing materials in place.

Estimating the material and labor costs for such a roof requires careful calculations based on the roof area, material coverage, and labor rates. This blog explains how to calculate the required materials and total costs step by step, complete with formulas and examples.

Estimate the material and cost

Step 1: Calculate the Roof Area

To find the total area of the roof, multiply the length and width of the roof:

$\text{Roof Area} = \text{Length} \times \text{Width}$

Example:

If the roof is 30 feet long and 20 feet wide:

$\text{Roof Area} = 30 \, \text{ft} \times 20 \, \text{ft} = 600 \, \text{sq ft}$

Step 2: Calculate the Tar Needed

The amount of tar required depends on the roof area and the coverage rate of tar (tar needed per unit area):

$\text{Tar Needed} = \text{Roof Area} \times \text{Tar Coverage Rate}$

Example:

If the tar coverage rate is 0.5 gallons per square foot:

$\text{Tar Needed} = 600 \, \text{sq ft} \times 0.5 \, \text{gallons/sq ft} = 300 \, \text{gallons}$

Step 3: Calculate the Cost of Tar

To find the cost of tar, multiply the amount of tar needed by the cost per gallon of tar:

$\text{Tar Cost} = \text{Tar Needed} \times \text{Cost Per Gallon}$

Example:

If the cost of tar is $10 per gallon:

$\text{Tar Cost} = 300 \, \text{gallons} \times 10 \, \text{\$/gallon} = 3000 \, \text{\$}$

Step 4: Calculate the Gravel Needed

The amount of gravel required is calculated similarly to tar:

$\text{Gravel Needed} = \text{Roof Area} \times \text{Gravel Coverage Rate}$

Example:

If the gravel coverage rate is 1 pound per square foot:

$\text{Gravel Needed} = 600 \, \text{sq ft} \times 1 \, \text{lb/sq ft} = 600 \, \text{lb}$

Step 5: Calculate the Cost of Gravel

Multiply the gravel needed by the cost per pound:

$\text{Gravel Cost} = \text{Gravel Needed} \times \text{Cost Per Pound}$

Example:

If the cost of gravel is $0.50 per pound:

$\text{Gravel Cost} = 600 \, \text{lb} \times 0.50 \, \text{\$/lb} = 300 \, \text{\$}$

Step 6: Calculate the Labor Cost

The labor cost depends on the roof area and labor cost per square foot:

$\text{Labor Cost} = \text{Roof Area} \times \text{Labor Cost Per Square Foot}$

Example:

If the labor cost is $2 per square foot:

$\text{Labor Cost} = 600 \, \text{sq ft} \times 2 \, \text{\$/sq ft} = 1200 \, \text{\$}$

Step 7: Calculate the Total Cost

The total cost is the sum of the tar cost, gravel cost, and labor cost:

$\text{Total Cost} = \text{Tar Cost} + \text{Gravel Cost} + \text{Labor Cost}$

Example:

$\text{Total Cost} = 3000 \, \text{\$} + 300 \, \text{\$} + 1200 \, \text{\$} = 4500 \, \text{\$}$

Conclusion

The Tar and Gravel Roof Calculator helps you quickly estimate the materials and costs for your roofing project. By following these formulas and examples, you can determine the tar, gravel, and labor costs accurately, ensuring that your project stays within budget.

Frequently Asked Questions

What are the advantages of a tar and gravel roof?

Built-up roofs use multiple layers, which can provide redundancy in the roofing system. The aggregate surface can also protect the roof membrane from weather and sunlight exposure.

Is a tar and gravel roof fire-resistant?

Fire performance applies to the complete tested roof assembly, not simply the gravel surface. Check the fire classification and local requirements for the exact roof system you plan to install.

How long does a tar and gravel roof last?

Service life varies based on the roof assembly, installation quality, weather exposure, drainage, maintenance, foot traffic, and repairs. Ask the manufacturer and installer about the expected service life and warranty for the specific system.

Does a tar and gravel roof need maintenance?

Yes. Regular professional inspections can help identify loose aggregate, damaged flashing, drainage problems, ponding water, and membrane issues before they become major leaks.

Can I use this calculator for a roof replacement?

Yes. Include removal, disposal, repairs, permits, and other replacement expenses in the additional-cost field for a more complete estimate.

Does the calculator include insulation or deck repair?

No, unless you add those amounts as additional costs. Calculate insulation upgrades, deck replacement, drainage changes, and structural repairs separately.

Is the calculator result a contractor quote?

No. It is a preliminary budget estimate. Obtain detailed quotes from qualified roofing contractors before starting the project.

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