diff --git a/templates/macros.html b/templates/macros.html
index fec5da9..50e55cf 100644
--- a/templates/macros.html
+++ b/templates/macros.html
@@ -3,6 +3,10 @@
 {% macro display_date(dt) %}{{ dt.strftime("%a %-d %b %Y") }}{% endmacro %}
 {% macro display_date_no_year(dt) %}{{ dt.strftime("%a %-d %b") }}{% endmacro %}
 
+{% macro format_distance(distance) %}
+  {{ "{:,.0f} km / {:,.0f} miles".format(distance, distance / 1.60934) }}
+{% endmacro %}
+
 {% macro trip_link(trip) %}
     <a href="{{ url_for("trip_page", start=trip.start.isoformat()) }}">{{ trip.title }}</a>
 {% endmacro %}