diff --git a/docs/options.md b/docs/options.md
index 4fa6947..72b7659 100644
--- a/docs/options.md
+++ b/docs/options.md
@@ -49,6 +49,12 @@ This dropdown allows you to select how numbers (vote totals, etc.) are represent
 * Rational: Numbers are represented exactly as fractions, resulting in the elimination of rounding error, but increasing computational complexity when the number of surplus transfers is very large.
 * Native: Numbers are represented as native integers or floating-point numbers. This is fast, but not recommended as unexpectedly large rounding errors may be introduced in some circumstances.
 
+### Round votes/ballot weights to [n] d.p. (--round-votes, --round-weights)
+
+When rounding is enabled, the votes credited to candidates during surplus transfers and exclusions, and/or the weights of the ballot papers, are rounded to the specified number of decimal places.
+
+This enables, for example, votes to be counted only in integers, while ballot weights and transfer values are calculated to higher precision (according to the Numbers) option.
+
 ## Surplus order (-s/--surplus-order)
 
 This dropdown allows you to select in what order surpluses are distributed: