diff --git a/include/boost/url/impl/scheme.ipp b/include/boost/url/impl/scheme.ipp
index d8561837..a19ce19e 100644
--- a/include/boost/url/impl/scheme.ipp
+++ b/include/boost/url/impl/scheme.ipp
@@ -107,6 +107,25 @@ to_string(scheme s) noexcept
     return "<unknown>";
 }
 
+std::uint16_t
+default_port(scheme s) noexcept
+{
+    switch(s)
+    {
+    case scheme::ftp:
+        return 21;
+    case scheme::http:
+    case scheme::ws:
+        return 80;
+    case scheme::https:
+    case scheme::wss:
+        return 443;
+    default:
+        break;
+    }
+    return 0;
+}
+
 } // urls
 } // boost
 
diff --git a/include/boost/url/scheme.hpp b/include/boost/url/scheme.hpp
index 666d8392..27d37845 100644
--- a/include/boost/url/scheme.hpp
+++ b/include/boost/url/scheme.hpp
@@ -12,6 +12,7 @@
 
 #include <boost/url/detail/config.hpp>
 #include <boost/url/string_view.hpp>
+#include <cinttypes>
 
 namespace boost {
 namespace urls {
@@ -150,6 +151,29 @@ BOOST_URL_DECL
 string_view
 to_string(scheme s) noexcept;
 
+/** Return the default port for a known scheme
+
+    This function returns the default port
+    for the known schemes. If the value does
+    not represent a known scheme or the scheme
+    does not represent a protocol, the function
+    returns zero.
+
+    The following ports are returned by the
+    function:
+
+    @li @ref scheme::ftp = 21
+    @li @ref scheme::http, @ref scheme::ws = 80
+    @li @ref scheme::https, @ref scheme::wss = 443
+
+    @return An integer with the default port number
+
+    @param s The known scheme constant
+*/
+BOOST_URL_DECL
+std::uint16_t
+default_port(scheme s) noexcept;
+
 } // urls
 } // boost
 
diff --git a/test/unit/scheme.cpp b/test/unit/scheme.cpp
index de08c2ed..ece3a64c 100644
--- a/test/unit/scheme.cpp
+++ b/test/unit/scheme.cpp
@@ -124,6 +124,15 @@ public:
         check("gopher");
         check("magnet");
         check("mailto");
+
+        BOOST_TEST_EQ(default_port(scheme::none), 0);
+        BOOST_TEST_EQ(default_port(scheme::unknown), 0);
+        BOOST_TEST_EQ(default_port(scheme::ftp), 21);
+        BOOST_TEST_EQ(default_port(scheme::file), 0);
+        BOOST_TEST_EQ(default_port(scheme::http), 80);
+        BOOST_TEST_EQ(default_port(scheme::https), 443);
+        BOOST_TEST_EQ(default_port(scheme::ws), 80);
+        BOOST_TEST_EQ(default_port(scheme::wss), 443);
     }
 };