Organic, Mechanical and Musical Proportions
From The Elements of Typographic Style by Robert Bringhurst.
Double Square 2
Tall Octagon 1.924
Tall Hexagon 1.866
Octagon 1.848
Hexagon ~1.732
Tall Pentagon 1.701
Golden Section ~1.618
Pentagon ~1.539
Short Pentagon 1.376
Tall Half Octagon 1.307
Half Octagon 1.207
Truncated Pentagon ~1.176
Turned Hexagon 1.155
Tall Cross Octagon 1.082
Turned Pentagon 1.051
Square 1
Broad Pentagon 0.951
Broad Cross Octagon 0.924
Broad Hexagon 0.866
Full Cross Octagon 0.829
ISO ~1.414
Octave 2 C – C
Major 7th 1.875 C – B
Minor 7th 1.778 C – B♭
Major 6th ~1.667 C – A
Minor 6th 1.6 C – A♭
Fifth 1.5 C – G
Diminished 5th ~1.414 C – G♭
Augmented 4th ~1.414 C – F♯
Fourth ~1.333 C – F
Major 3rd 1.25 C – E
Minor 3rd 1.2 C – E♭
Major 2nd 1.125 C – D
Minor 2nd ~1.067 C – D♭
Unison 1 C – C