Roof Ridge Height Calculator

A roof ridge height calculator compares the ridge height across roof types — Gable, Hip, Shed, Gambrel, and Mansard — and also estimates roof size (sloped length, ridge length, and total area) from the span, pitch, and overhang. This page is that tool: pick a roof type to see its ridge height formula and a live example, then run the size estimator for area and length. It differs from a plain roof height calculator, which only returns the single gable rise from span and pitch; this page adds the type comparison and the roof-size estimation.

Enter the span (feet) and pitch (X/12) at the top, then click a roof-type card — Gable, Hip, Shed, Gambrel, or Mansard. The card highlights and shows that type’s ridge height for your span and pitch. A shed roof will show roughly double the gable ridge height because it slopes across the full span; a hip roof matches the gable height but with a shorter ridge. Use the filter to compare types side by side before choosing a roof form for a zoning or clearance target.

The size estimator at the top takes span, pitch, overhang, and building length and returns the ridge height, the sloped rafter length (run plus overhang divided by the cosine of the pitch angle), the ridge length (building length plus two overhangs), and the total gable roof area (two planes times slored length times ridge length). That makes the page a roof size estimator — you get the height, the length, and the area in one pass, which is what most calculate-size-of-roof questions actually need.

To calculate the size of a roof, you need three linked dimensions: the ridge height = (span / 2) × (X / 12); the sloped rafter length = (run + overhang) ÷ cos(pitch angle) where the pitch angle = atan(X / 12); and the total roof area = 2 × sloped length × ridge length for a gable. The roof length calculator portion of this page computes the sloped length and ridge length from your span, overhang, and building length, so you can calculate the size of a roof for shingle orders or sheathing takeoff in one place.

A shed roof has roughly double the ridge height of a gable roof at the same span and pitch, because the shed slopes across the full span while the gable slopes across half the span. For a 24-foot span at 6/12, a gable peaks at 6' 0" while a shed peaks at 12' 0" on the high side. That is the single biggest reason to use a roof ridge height calculator that compares types rather than a single-formula roof rise calculator — the same span and pitch give very different heights depending on the roof form.

The roof length calculator is the part of the size estimator that returns the sloped rafter length — the distance along the slope from the ridge to the fascia, including the overhang. It is computed as (run + overhang) ÷ cos(pitch angle), where run = span / 2 and the pitch angle = atan(X / 12). For a 24-foot span at 6/12 with a 1-foot overhang, that is (12 + 1) ÷ cos(26.57°) ≈ 14.54 feet of sloped rafter per side. This is the roof length you use to order rafter stock and sheathing.

The roof dimension calculator returns geometric dimensions for planning and takeoff — ridge height, sloped length, ridge length, and area. For a shingle order the area number is the right starting point, but add a waste factor (typically 10–15% for a simple gable, more for hips and valleys) and confirm against the actual roof plan, because hips, valleys, dormers, and rake details all add area that the simple gable formula does not capture. Treat the output as a planning estimate, not a cut order.

Because the hip rafter slopes in from the corner but the main ridge still sits at the center of the span at the same pitch. So the ridge height of a hip roof equals the gable ridge height — (span / 2) × (X / 12) — for the same span and pitch. What changes on a hip roof is the ridge length (it is shorter, because the hip rafters eat into the building length at both ends) and the number of planes (four instead of two). The roof ridge height calculator on this page keeps the height the same and flags the ridge-length difference in the hip card note.

Yes, with a caveat. The gambrel and mansard cards show an illustrative ridge height based on a standard two-pitch split (a steep lower pitch and a shallow upper pitch over equal quarter-span runs). Because real gambrel and mansard designs mix pitches freely, the live number is a planning estimate, not an exact value — for an exact ridge height on a specific gambrel or mansard design, compute each segment’s rise separately (lower rise + upper rise) from the actual pitches and runs on the plans. The card note flags this as an Edge Case for that reason.