diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index fc0b9cd99f..4f3930465d 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -552,7 +552,7 @@ inline ESPHOME_ALWAYS_INLINE uint32_t fast_div1000_32(uint64_t us) {
   uint32_t lo = static_cast<uint32_t>(us);
   uint32_t hi = static_cast<uint32_t>(us >> 32);
   // Combine remainder term: hi * (2^32 % 1000) + lo
-  // Note: hi * R fits in uint32_t when hi < UINT32_MAX / R (~14.5M), i.e. us < ~62 quadrillion
+  // Safe for us < (14510024 << 32), i.e. ~6.2e16 (~1,975 years of microseconds)
   uint32_t adj = hi * R + lo;
   // If adj overflowed, the true value is 2^32 + adj; apply the identity again
   return hi * Q + (adj < lo ? (adj + R) / D + Q : adj / D);