Percentile Pair

The d% die type represents a percentile pair — a tens die (00, 10, 20…90) and a units die (0–9) rolled together. This is how percentile dice are physically rolled at the table.

The 00+0=100 Rule

When both the tens die and units die show 0, the result is 100, not 0. This is the standard convention in Call of Cthulhu and most d100 systems.

Relationship to d100

See d% vs d100 for the full comparison. In brief:

• d% is a linked pair where kh/kl operates on the tens die only
• d100 is a flat 1–100 die where kh/kl operates on the whole value

Call of Cthulhu Usage

Roll	Notation
Standard skill check	d%
One bonus die	2d%kl
Two bonus dice	3d%kl
One penalty die	2d%kh
Two penalty dice	3d%kh

Display

The result popup should show the percentile pair components:

• d% → shows “70 + 3 = 73”
• 2d%kl → shows “70, 40, 3 = 43” (kept the 40, dropped the 70)

See also: d% vs d100, Keep Highest and Lowest, Notation Spec