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How much flat roof will my rolls of EPDM cover?

EPDM rubber roofing goes down in big sheets, and the count follows the roof's area and the roll's size. Enter the rolls you have and the flat roof they cover comes back at the calculator's 10 by 50 foot roll, about 46.5 m² — with no allowance for seams, upturns or flashings, which is the first thing to take back off.
  • 5 rollsThe example worked below
  • EPDM Single-Ply Roofing Roll CalculatorEvery figure is its own

You have

How much EPDM membrane?

rolls

Worked by the EPDM Single-Ply Roofing Roll Calculator at the settings below.

Saved amounts stay in this browser.

The settings it uses

Roll coverage area
500 sq ft

What it will do

2,500 sq ft of roof

232 m²

  1. One flat roof. Enough for a flat roof about 50 × 50 ft.

  2. Or several. About 1 flat roof of the size the EPDM Single-Ply Roofing Roll Calculator opens on: a flat roof about 46 × 46 ft.

Check it forwards

Roof Area
2,500 sq ft
It asks for
5 rolls
You have
5 rolls

The EPDM Single-Ply Roofing Roll Calculator asks for 5 rolls at that size, and 6 rolls one step larger.

Open this in the EPDM Single-Ply Roofing Roll Calculator

If you had more, or less

Around your amount

Each worked by the EPDM Single-Ply Roofing Roll Calculator at the same settings.

  1. Half

    3 rolls

    1,500 sq ft

    a flat roof about 39 × 39 ft

  2. Yours

    5 rolls

    2,500 sq ft

    a flat roof about 50 × 50 ft

  3. Half as much again

    8 rolls

    4,000 sq ft

    a flat roof about 63 × 63 ft

  4. Double

    10 rolls

    5,000 sq ft

    a flat roof about 71 × 71 ft

Common amounts

What each amount of EPDM membrane covers

The sizes it is usually sold in, each worked by the EPDM Single-Ply Roofing Roll Calculator at the settings above.

You haveIt coversAs one flat roofAverage flat roofs
1 roll500 sq ft(46.5 m²)a flat roof about 22.4 × 22.4 ftunder 1
2 rolls1,000 sq ft(92.9 m²)a flat roof about 32 × 32 ftunder 1
5 rolls2,500 sq ft(232 m²)a flat roof about 50 × 50 ft1
10 rolls5,000 sq ft(465 m²)a flat roof about 71 × 71 ft2

Ten by fifty is five hundred square feet

The calculator divides the roof by one roll's coverage — a common EPDM roll is about 10 by 50 feet, 500 square feet (46.5 m²) — and rounds up. Read backwards, five rolls cover 2,500 square feet (232.5 m²), a roof about 50 feet (15.2 m) square. Nothing is added for the seams, the turn-up at walls and curbs, or the flashing pieces, so the roof a pile of rolls really finishes is smaller.

Wider sheets, fewer seams

Roll width decides how much seam a roof has. Covering the same area in wider sheets roughly halves the length of field seam, and seams are where single-ply roofs leak — a bare coverage area hides that trade-off completely. EPDM is also sold in larger sheets and cut pieces, so on a small roof a single sheet with no field seam at all may be the better buy than a count of standard rolls.

Thickness and hold-down are separate

The same roll count buys 45, 60 or 90 mil sheet (about 1.1, 1.5 or 2.3 mm), reinforced or not, and thickness is what the warranty term and the hail and foot-traffic tolerance key off. Fully adhered, mechanically attached and ballasted roofs need different adhesive, plates and fasteners or ballast, denser in the perimeter and corner zones — usually the larger part of the order, and none of it follows from area.

How the answer is worked

Nothing here is a second formula. The EPDM Single-Ply Roofing Roll Calculator runs forwards — a size in, a quantity out — and this page grows its own starting flat roof in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.

Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.

EPDM Single-Ply Roofing Roll Calculator

runs it forwards

Calculate how many rolls of EPDM single-ply membrane are needed for a roof area.

Work out what to buy instead

Solve backwards

Other things you might already have

Solve backwards

Start from what is already in the yard

Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.

Every Solve Backwards pageEPDM Single-Ply Roofing Roll Calculator

  • The calculator's own figures

    Nothing is estimated twice: the page runs the same calculator you would order with.

  • The largest size that fits

    Where a calculator rounds up to whole containers, the answer stops before the next one.

  • Both unit systems

    Gallons and litres, square feet and square metres, side by side.

Frequently asked questions

How much roof does 5 rolls of EPDM membrane cover?
At the EPDM Single-Ply Roofing Roll Calculator's own settings, 2,500 sq ft (232 m²) — a flat roof about 50 × 50 ft. That is about 1 flat roof of the size the calculator opens on: a flat roof about 46 × 46 ft. Every figure follows the settings, which you can change in the calculator.
How many square feet is a roll of EPDM?
A common roll is about 10 by 50 feet, 500 square feet (46.5 m²), which is the calculator's default. EPDM is also sold in wider and longer sheets and in cut-to-size pieces, so enter the coverage of the roll you are actually buying.
How many rolls of EPDM for a 20 by 30 foot roof?
600 square feet (55.7 m²) divided by 500 is 1.2, so 2 rolls by the calculator's count — before the upturn at walls and curbs, which can push a roof close to a whole roll over the line. A wider sheet may cover it with one seam or none, which is worth pricing.
What thickness of EPDM should I use?
It is sold at 45, 60 and 90 mil (about 1.1, 1.5 and 2.3 mm). Thickness sets the warranty term and the tolerance for hail and foot traffic; the area arithmetic is identical for all three, so the roll count cannot choose it — the roof's use, the warranty wanted and the maker's system do.