diff --git a/internal/sync/locators.go b/internal/sync/locators.go
index 28acdda..c371226 100644
--- a/internal/sync/locators.go
+++ b/internal/sync/locators.go
@@ -58,6 +58,13 @@ func cachedConverter(epubPath string) *CFIConverter {
 	return c
 }
 
+// SectionPercentageCached resolves the spine-section percentage of a CRE
+// xpointer through the shared bounded converter cache, so per-annotation
+// lookups parse the EPUB once per book instead of once per annotation.
+func SectionPercentageCached(epubPath, xpointer string) float64 {
+	return cachedConverter(epubPath).SectionPercentage(xpointer)
+}
+
 func ConvertToCanonical(
 	source LocatorSource,
 	devicePos string,