Communi, Decimum Saeculum (isopsephia)

Communi, Decimum Saeculum (Tenth Century Common) is a system of converting Latin letters to defined numeric values, seemingly based on Hebrew-to-Latin correspondences, as observed by John Opsopaus in his reading of manuscripts from the 10th and 11th centuries. Unlike in Greek isopsephy or Hebrew gematria, where the conversions are based on classical utilisation of every glyph as both a letter and a numeral, Latin only utilised a limited set of letters in combinations as ordinary numbers (I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000), and consequently the conversions are not based on routine equivalencies but rather assumed correspondences with other languages.

Conversion Table

Letter	Value
A, a	1
B, b	2
C, c	3
D, d	4
E, e	5
F, f	7
G, g	8
H, h	9
I, i	10
J, j	10
K, k	20
L, l	30
M, m	30
N, n	50
O, o	60
P, p	70
Q, q	80
R, r	100
S, s	200
T, t	300
U, u	400
V, v	400
W, w	400
X, x	500
Y, y	600
Z, z	700

Tools

• https://hatch.kookscience.com/cipher/iso.php?cipher=la_5