diff --git a/include/zephyr/usb/usb_ch9.h b/include/zephyr/usb/usb_ch9.h
index 8ecadf64bd8..0c4a3ac0608 100644
--- a/include/zephyr/usb/usb_ch9.h
+++ b/include/zephyr/usb/usb_ch9.h
@@ -354,8 +354,8 @@ struct usb_association_descriptor {
 /** Calculate high speed interrupt endpoint bInterval from a value in microseconds */
 #define USB_HS_INT_EP_INTERVAL(us)	CLAMP((ilog2((us) / 125U) + 1U), 1U, 16U)
 
-/** Calculate high speed isochronous endpoint bInterval from a value in microseconds */
-#define USB_FS_ISO_EP_INTERVAL(us)	CLAMP(((us) / 1000U), 1U, 16U)
+/** Calculate full speed isochronous endpoint bInterval from a value in microseconds */
+#define USB_FS_ISO_EP_INTERVAL(us)	CLAMP((ilog2((us) / 1000U) + 1U), 1U, 16U)
 
 /** Calculate high speed isochronous endpoint bInterval from a value in microseconds */
 #define USB_HS_ISO_EP_INTERVAL(us)	CLAMP((ilog2((us) / 125U) + 1U), 1U, 16U)