Why new String with UTF-8 contains more bytes

byte bytes[] = new byte[16];
random.nextBytes(bytes);
try {
   return new String(bytes, "UTF-8");
} catch (UnsupportedEncodingException e) {
   log.warn("Hash generation failed", e);
}

When I generate a String with given method, and when i apply string.getBytes().length it returns some other value. Max was 32. Why a 16 byte array ends up generating a another size byte string ?

But if i do string.length() it returns 16.