diff --git a/sys/fmt/fmt.c b/sys/fmt/fmt.c
index adffd46868..0d012ed1cc 100644
--- a/sys/fmt/fmt.c
+++ b/sys/fmt/fmt.c
@@ -53,6 +53,20 @@ static inline char _to_lower(char c)
     return 'a' + (c - 'A');
 }
 
+int fmt_is_number(const char *str)
+{
+    if (!str || !*str) {
+        return 0;
+    }
+    for (; *str; str++) {
+        if (!fmt_is_digit(*str)) {
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
 size_t fmt_byte_hex(char *out, uint8_t byte)
 {
     if (out) {
diff --git a/sys/include/fmt.h b/sys/include/fmt.h
index c201645593..8e89906ef8 100644
--- a/sys/include/fmt.h
+++ b/sys/include/fmt.h
@@ -69,6 +69,15 @@ static inline int fmt_is_upper(char c)
     return (c >= 'A' && c <= 'Z');
 }
 
+/**
+ * @brief   Test if the given string is a number (regex `[0-9]+`)
+ *
+ * @param[in] str   String to test, **must be `\0` terminated**
+ *
+ * @return  true if @p str solely contains digits, false otherwise
+ */
+int fmt_is_number(const char *str);
+
 /**
  * @brief Format a byte value as hex
  *