How to Measure Asphalt for Sealcoat: Net Area in Square Feet

Measuring asphalt for sealcoat means finding one number: the net area of asphalt that will be sealed, in square feet. Walk the outline, sketch it, split it into simple shapes, add those shapes, and subtract anything inside the outline that will stay unsealed. That net area is the number the product and ordering steps need.

How do you measure asphalt for sealcoat?

Measure every sealed section in feet, work out each section with one shape formula, add the sections, and subtract the unsealed areas. Record the result as a single net area in square feet, with the sketch and the section list kept beside it. A single guessed total cannot be checked. A section list can.

What do you need before you start measuring?

Use a long tape or a measuring wheel. A tape suits a small driveway. A wheel suits a large lot, because it follows curves and long edges without sagging between two people. Carry chalk or marking paint to mark section corners, and paper for the sketch. Measure on the pavement itself, following its edges and curves, rather than estimating from a kerb or a fence line.

Draw the outline before you write down any number. Mark each corner, each curve, each island, and each strip that will stay unsealed. Label every section with a letter, such as A, B, and C, and write each dimension next to its section on the sketch. The sketch is the record that lets someone else repeat the measurement and reach the same total.

Which formula fits each shape?

Record every dimension in feet. Convert inches by dividing by 12, so 12 ft 6 in becomes 12.5 ft. Keep one unit through the whole record. Mixing feet and metres in one section list is a common source of a wrong total, and it is hard to spot after the sections are added.

How do you handle curves, flares, and islands?

Split an irregular outline into sections that cover it exactly once. An L-shaped drive becomes two rectangles that meet at a shared edge but do not overlap. A curved turnaround becomes a semicircle plus the rectangles it joins. A flare at the street becomes a triangle. Each section gets its own letter on the sketch, and the shared edges are marked so the same ground is never counted twice.

Measure a curve along the pavement edge with the wheel, or fit a semicircle or triangle to it and measure the radius, base, and height that the formula needs. A straight line across a curve, from one end to the other, shortens the measurement, because it cuts across ground that will be sealed. Where a curve fits no simple shape, split it into short straight sections and add them, and note that approximation on the sketch.

Subtract every unsealed area inside the outline as its own line. A planting island, a concrete pad, a concrete walk strip, and a building footprint inside a lot all come off the gross total. The deduction method also works the other way round: measure a whole rectangular lot, then subtract the building and every unsealed area, and the remainder is the sealed area. Either route must reach the same net total when the same outline is measured.

What does a worked measurement look like?

Fixture drive with a pad, a flare, a turnaround, and two deductions. The sections are:

• Section A, driveway rectangle: 48 ft x 12 ft = 576 ft2.
• Section B, parking pad rectangle: 20 ft x 18 ft = 360 ft2.
• Section C, street flare triangle: 1/2 x 8 ft x 6 ft = 24 ft2.
• Section D, turnaround semicircle: 1/2 x 3.1416 x 6 ft x 6 ft = 56.5 ft2, rounded to one decimal place before summing.

Gross sealed area is 576 + 360 + 24 + 56.5 = 1,016.5 ft2. The deductions are a planting island of 8 ft x 5 ft = 40 ft2 and a concrete walk strip of 12 ft x 3 ft = 36 ft2, for 76 ft2 in total. Net sealed area is 1,016.5 - 76 = 940.5 ft2.

A smaller drive checks the same way. A rectangle of 40 ft x 15 ft gives 600 ft2. A concrete pad of 10 ft x 6 ft inside it gives a 60 ft2 deduction. Net sealed area is 600 - 60 = 540 ft2.

How do you convert the result?

Keep the square-foot figure as the controlling record. Converted figures are for quotes or records that use other units, and they are rounded to one decimal place after conversion.

What do you check before the area goes to ordering?

• Re-measure the longest dimension. A single wrong long edge moves the total more than any other single error.
• Add the sections again from the sketch, and check that no two sections overlap.
• Check the net total against the whole lot rectangle. A net area larger than the lot that contains it means a section was counted twice or a deduction was missed.
• List every deduction with its own dimensions, so an unsealed area is never silently dropped from the record.
• Record the planned coat count on a separate line, such as 2 coats planned. The surface area stays 940.5 ft2 in the fixture example whatever the coat count is. Coats change the purchase quantity, and that multiplication belongs to the ordering step.
• Mark any area that will stay unsealed in this round as a deduction, and keep it on the sketch for the next round.
• Note the basis of the measurement when comparing quotes: measured on the pavement, in feet, with the section list attached. A quote based on a different basis, such as an aerial estimate, will differ, and the difference is a measurement difference, not necessarily a price difference.

Which measurement mistakes change the result?

• Measuring the lot instead of the asphalt, and forgetting the building, lawn, and gravel deductions.
• Counting the corner square twice where two rectangles meet in an L shape.
• Measuring across a curve with a straight line instead of along the pavement edge.
• Guessing a section instead of measuring it, then treating the guess as a measured figure.
• Mixing feet and metres, or feet and inches without converting, in one section list.
• Leaving a concrete pad, island, or walk strip inside the gross total.
• Adding coats into the surface area, so the area itself is inflated before ordering starts.
• Measuring once, with no sketch, so no one can repeat or check the total.
• Using a rounded section figure in the middle of the sum without noting it, then wondering why a second measurement differs by a few square feet.

What this page does not decide

Product choice, coverage rate, waste allowance, pack rounding, and price belong to other pages and to the chosen product label. SealMaster product data shows why a single rate cannot be fixed here: its PMCTS concentrate covers approximately 85 to 95 sq ft per gallon per coat as a sand-filled coat, while its coal tar concentrate covers approximately 100 to 120 sq ft per gallon per coat, and both notes say coverage varies with pavement age and porosity. Cure time, crack filling, oil-spot treatment, and application conditions also belong to the product guide and the product label for the sealer being used. No measurement on this page approves a pavement, a drainage layout, or a coating system on its own.