d% vs d100

These are distinct die types in FlowDice with different behavior. This distinction matters for lowest operations.

d100 — Flat Die

A single die producing 1–100. No internal structure.

2d100kl rolls two independent d100 results and keeps the lowest complete value. Both the tens and units are rerolled for each die.

d% — Percentile Pair

A linked pair: tens die (00, 10, 20…90) + units die (0–9). The 00+0=100 rule applies — when both show zero, the result is 100, not 0.

2d%kl rolls an extra tens die and keeps the lowest tens digit. The units die is rolled once and stays fixed. This is the Call of Cthulhu bonus die mechanic.

Why Both Exist

The distinction matters because CoC bonus/penalty dice only swap the tens digit:

• Roll d% → get 73 (tens: 70, units: 3)
• Bonus die rolls an extra tens: 40
• Keep lower tens → result is 43 (the 3 is locked)

With 2d100kl, you’d get two completely independent rolls (73 and 41) and keep 41 — a different distribution.

Summary

Type	What 2dXkl does	Use case
d100	Two independent 1–100 rolls, keep lowest	Generic “lowest of two percentile rolls”
d%	One extra tens die, keep lowest tens, units fixed	CoC bonus die

See also: Keep Highest and Lowest, Notation Spec