Roof Rise Calculator

Calculate the total roof rise (peak height above the top plate) from pitch and building span or measurements

Calculate roof rise from building span and roof pitch

Quick presets

ft

Total Roof Area

0 sq ft

0.0 roofing squares • Pitch multiplier: 1.054

PRO

Professional Calculator

Calculate total area for complex roofs with multiple sections

ft
ft

Total Roof Area

1,389 sq ft

Sections

2

Total Squares

13.9

Cost Breakdown

Section 1: $1,054 (76%)
Section 2: $335 (24%)

Detailed Breakdown

Section 11,054 sq ft
Dimensions40 × 25 ft (footprint: 1,000 sq ft)
Pitch4/12 (×1.054)
Section 2335 sq ft
Dimensions20 × 15 ft (footprint: 300 sq ft)
Pitch6/12 (×1.118)
Total Roof Area1,389 sq ft
Total Squares13.9
Bundles (10% waste)46
How to Use This Calculator
Using the Roof Rise Calculator provides the vertical peak height for framing, zoning, and attic planning:

From Pitch tab: Enter your building span (eave-to-eave width) and select the roof pitch. The calculator divides the span by 2 to get the run, then multiplies by the pitch ratio to determine the rise. It also shows the total ridge height when you enter the wall height. Use this when planning new construction or evaluating how different pitches affect the overall building height for zoning compliance.

From Measurements tab: If you measured the vertical rise and horizontal run inside an existing attic (or from elevation drawings), enter those values. The calculator determines the pitch ratio, angle in degrees, and slope percentage. This is useful when you need the exact pitch of an existing roof for renovation planning or insurance documentation.

Attic Space tab: Enter the building span, length, and pitch to see the total roof rise and the usable attic floor area at your chosen minimum headroom. The calculator determines how far from the center the roof slope reaches the minimum height, then calculates the rectangular usable zone. This helps you evaluate whether a roof has enough volume for a finished attic, bonus room, or storage area.

The Formula
The roof rise formulas are:

Rise from Pitch: Run = Building Span / 2 Rise = Run x (Pitch Rise / 12) Total Ridge Height = Foundation + Wall Height + Rise

Pitch from Measurements: Pitch = (Measured Rise / Measured Run) x 12 Expressed as: Pitch/12

Rafter Length (slant): Rafter Length = sqrt(Run^2 + Rise^2) Or: Rafter Length = Run x sqrt(1 + (Pitch/12)^2)

Usable Attic Width (at minimum headroom h): Distance from eave where height = h: d = h / (Pitch/12) Usable width = Span - 2d (must be > 0) Usable floor area = Usable Width x Building Length

Example pitch multipliers: - 4/12: Rise = Run x 0.333, Rafter = Run x 1.054 - 6/12: Rise = Run x 0.500, Rafter = Run x 1.118 - 8/12: Rise = Run x 0.667, Rafter = Run x 1.202 - 10/12: Rise = Run x 0.833, Rafter = Run x 1.302 - 12/12: Rise = Run x 1.000, Rafter = Run x 1.414
Example Calculation
Example: Calculating Rise for a New Construction Home in Texas

Mike is building a 30 ft wide single-story home with a 6/12 pitch roof and 9-foot walls.

Step 1: Calculate run
• Run = Building Span / 2 = 30 / 2 = 15 feet

Step 2: Calculate rise
• Rise = Run x (Pitch Rise / 12) = 15 x (6/12) = 15 x 0.5 = 7.5 feet

Step 3: Calculate total ridge height
• Foundation to top plate: 1.5 ft (foundation + floor system) + 9 ft walls = 10.5 ft
• Ridge height: 10.5 + 7.5 = 18.0 ft from ground to ridge
• (HOA maximum is 25 ft — compliant with margin)

Step 4: Calculate rafter length
• Rafter = sqrt(15^2 + 7.5^2) = sqrt(225 + 56.25) = sqrt(281.25) = 16.77 ft
• Add 1.5 ft for eave overhang: 18.27 ft rafters (use 20 ft lumber)

Step 5: Evaluate attic space
• At 5 ft minimum height: distance from eave = 5 / 0.5 = 10 ft
• Usable width: 30 - 2(10) = 10 ft
• With 40 ft building length: 10 x 40 = 400 sq ft of storage space at 5+ ft headroom
• At 7.5 ft (habitable): distance = 7.5 / 0.5 = 15 ft, usable width = 0 ft (ridge just barely reaches 7.5 ft)
• Not suitable for habitable attic at 6/12 on 30 ft span — need 8/12 or wider span

Frequently Asked Questions

How do I calculate roof rise from pitch and span?
The formula is: Rise = (Span / 2) x (Pitch Rise / 12). For a 30-foot span with a 6/12 pitch: Run = 30 / 2 = 15 feet. Rise = 15 x (6/12) = 15 x 0.5 = 7.5 feet. The ridge sits 7.5 feet above the wall top plates. To find the total height from ground to ridge, add the wall height (e.g., 8 ft walls + 7.5 ft rise = 15.5 ft total ridge height).
What is the difference between roof rise, roof height, and ridge height?
Roof rise is the vertical distance from the wall top plate to the ridge (peak). It depends only on pitch and run. Ridge height is the total height from ground level to the ridge peak, which includes the foundation, floor system, wall height, and roof rise. Roof height is sometimes used interchangeably with ridge height in building codes. For zoning and HOA purposes, ridge height is what matters. For example: 2 ft foundation + 8 ft walls + 7.5 ft rise = 17.5 ft ridge height.
What roof pitch gives enough rise for an attic bedroom?
Building codes (IRC R305) require at least 7.5 feet of ceiling height over at least 50% of the required floor area. For a 30-foot wide building, a 10/12 pitch produces a 12.5 ft rise, giving about 12 feet of width at 7.5 ft height — just enough for a small bedroom. An 8/12 pitch on the same span gives 10 ft of rise and roughly 6 feet of width at 7.5 ft height, which is too narrow for a bedroom. For practical attic living space, use 10/12 or steeper on buildings at least 28 feet wide.
How does roof rise affect material costs?
Greater roof rise means steeper pitch, which increases costs in three ways. First, steeper roofs have more surface area (a 12/12 pitch has 41% more area than a flat roof). Second, labor costs increase 15-35% for pitches above 8/12 due to safety equipment and slower work pace. Third, steeper pitches require more framing lumber for longer rafters and taller ridge boards. A 6/12 pitch on a 30 ft span needs 16.8 ft rafters; at 12/12 the same span needs 21.2 ft rafters — 26% more lumber.
Can I increase my roof rise without changing the pitch?
Yes, but only by increasing the building span (width). Rise is directly proportional to the run (half the span) at a given pitch. Alternatively, you can raise the knee walls (short walls on top of the second-floor joists in a Cape Cod or 1.5-story design) to add headroom without changing the roof pitch or span. A 4-foot knee wall effectively adds 4 feet of usable height along the walls while keeping the same roof geometry above.

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Related Guides & Resources

How to Measure a Roof Understanding Roof Pitch Roof Pitch Chart