Easy, No-Brainer 3-Step Roofing Estimator

Most roofing calculators and guides have you pulling out formulas and using the Pythagorean theorum and doing calculations with sliderules, when all you really want to know is two very simple things:

  • What’s the approximate size of my roof?
  • How much approximately will the $@!!*# roof cost?

Why won’t anyone tell that?  Beats me.  So, the caveat here is that, at the expense of finely granulated accuracy, we are giving you approximate roofing sizes and costs.  Average, after all, means after.  And while average roofing costs will not apply exactly to you, it will apply in a kinda-sorta way because…it’s average.  Got that?  The roofing contractors will howl in protest (I can already hear them):  But what about flashing, what about New England vs. Arizona, what about seasons?  They’re right, but unless they want to start handng out roofing estimates in an article, we’ll have to go with my calculations.  Now let’s get started.

Step 1. What’s the Approximate Roof Pitch?

Roof Pitch Examples

Break it down simple, and say that you’ve got either a low-pitched, medium-pitched, or steeply-pitched house.

Low-Pitch Roof

This can range from absolutely flat to sloped-but-still-easy-to-walk-on.  A rambler has this type of roof.

Medium-Pitch Roof

The “average” house.  It’s not a low-down 1960s rambler, but it’s not a Gothic-y Victorian, either.  This describes most contemporary houses.

Steep-Pitched Roof

Now we’re getting fancy.  You don’t need to have a historic hosue to have a steep roof, either.  Basically, this means that it’s next to impossible to walk on this roof.

Step 2. How Many Roofing Squares Will the Roof Need?

A roofing square is one-hundred square feet (100 sq. ft.) of shingles.

Because roofers use so many shingles at a time, it’s pointless for them to talk in units smaller than 100 square feet.  So, don’t confuse squares with square footage.

Example:  Your house has 1,200 square feet and a low pitched roof.  So, your total squares are 13.8.

House Square Footage Low Pitch Low to Medium Pitch Medium to High Pitch Steep Pitched
700 8.05 8.75 9.8 11.9
800 9.2 10 11.2 13.6
900 10.35 11.25 12.6 15.3
1000 11.5 12.5 14 17
1100 12.65 13.75 15.4 18.7
1200 13.8 15 16.8 20.4
1300 14.95 16.25 18.2 22.1
1400 16.1 17.5 19.6 23.8
1500 17.25 18.75 21 25.5
1600 18.4 20 22.4 27.2
1700 19.55 21.25 23.8 28.9
1800 20.7 22.5 25.2 30.6
1900 21.85 23.75 26.6 32.3
2000 23 25 28 34
2100 24.15 26.25 29.4 35.7
2200 25.3 27.5 30.8 37.4
2300 26.45 28.75 32.2 39.1
2400 27.6 30 33.6 40.8
2500 28.75 31.25 35 42.5
2600 29.9 32.5 36.4 44.2
2700 31.05 33.75 37.8 45.9
2800 32.2 35 39.2 47.6
2900 33.35 36.25 40.6 49.3
3000 34.5 37.5 42 51

Step 3. Figure the Roofing Cost

All estimated roofing costs include removal and disposal of existing shingles and installation of new shingles.  Labor and materials included.  Flashing, ice dams, underlayment, repairs, and related items not included.

Composition Shingle Roofing Estimate – Low End

Fiberglass 3-Tab 225 lb. 20 year

Multiply your squares by $143 per square cost.

Example:  35 squares x $143 = $5,005

Composition Shingle Roofing Estimate – High End

Architectural laminated 30 year

Multiply your squares by $171 per square cost.

Example:  35 squares x $171 = $5,985

Cedar Wood Roofing Estimate

16″ Red Label

Multiply your squares by $422 per square cost.

Example:  35 squares x $422 = $14,770

Slate Roofing Estimate

Pennsylvania slate

Multiply your squares by $812 per square cost.

Example:  35 squares x $812 = $28,420