The Original Blue Book
The page that turned trigonometry into a glance. One row per pitch, one column per cut: every common rafter and hip-valley length per foot of run, ready to multiply by your span.
Since 1925
Type your pitch and span. The rafter answers.
6/1226.6°
24ft
Common rafter length
13′ 5″ 1/16″
161.04″ per rafter · 13.42″ per ft of run × 12 ft of run
- Pitch
- 6/12
- Angle
- 26.6°
- Per ft of run
- 13.42″
Schematic geometry. Not to scale, true math, every pitch.
Length of Rafter per Foot Run (In Inches)
Length of Rafter per Foot Run (In Inches)
Rows
30
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 1/12
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 1/6
- Tail Cut loss "A"
- 2¾"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 1/4
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 1/3
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 5/12
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 1/2
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 7/12
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 2/3
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 3/4
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 5/6
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- 11/12
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- Full
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- ,
- Common Rafters
- Hip-Val Rafters
Angle in Deg.
- Rise
- Pitch
- ,
- Tail Cut loss "A"
- Common Rafters
- Hip-Val Rafters
A century of the same table.
The rafter length math hasn't changed since Albert Swanson printed it in 1925. The typography modernized, the columns reflowed, the cover got new ink. But the numbers a framer cuts to today are the numbers from the first edition.
| Rise | Pitch | Common rafter (per ft of run) | Hip / Valley (per ft of run) |
|---|---|---|---|
| 1.00″ | 12.04″ | 17.00″ | |
| 6.00″ | 1/4 | 13.42″ | 18.00″ |
| 8.00″ | 1/3 | 14.42″ | 18.76″ |
| 12.00″ | 1/2 | 16.97″ | 20.78″ |
| 16.00″ | 2/3 | 20.00″ | 23.32″ |
| 24.00″ | Full | 26.83″ | 29.39″ |
Same numbers Albert Swanson printed in 1925.
Open the full 1925 TableThe pocket book turned trigonometry into a glance. A framer who can find the number is a framer who never stops cutting.