Line Length Calculator | Ernesto Peña

LCA' = Length of lowercase alphabet (abcdefghijklmnopqrstuvwxyz + space) in points

Cρ = Desired character density (characters per line, including spaces)

S = Mathematical constant (0.0345 = 1/29 for Roman alphabet serif fonts)

Ll = Resulting line length in points

Upload a font file (.ttf, .otf, or .woff) and set your desired font size. The calculator will measure the lowercase alphabet with space and compute optimal line lengths for various character densities. Accuracy: ~5% for common serif typefaces.

1. Load Font

Upload Font File ↑ Choose Font File

Supported formats: .ttf, .otf, .woff, .woff2

Font Size

Calculated Metrics

LCA' (Lowercase Alphabet + Space)

—

S Constant

0.0345

2. Set Character Density

Cρ (Characters Per Line)

CPL

Including spaces

Current Calculation

Calculated Line Length

Upload a font to see results

Readability Benchmarks

Research-Based Ranges

Novice Readers (De Buen, 2014)

Range: 34-60 CPL | Optimal: 45 CPL

Expert Readers (De Buen, 2014)

Range: 45-80 CPL | Optimal: 60 CPL

Bringhurst Standard

Range: 45-75 CPL | Ideal: 66 CPL