diff --git a/sys/include/phydat.h b/sys/include/phydat.h
index 8a4e161f180d49e6c53f8bdde37683975ffe8711..e57a517c5436596b62e0d7a8e42242d1855282f6 100644
--- a/sys/include/phydat.h
+++ b/sys/include/phydat.h
@@ -110,7 +110,9 @@ enum {
     UNIT_PPB,       /**< part per billion */
     /* aggregate values */
     UNIT_TIME,      /**< the three dimensions contain sec, min, and hours */
-    UNIT_DATE       /**< the 3 dimensions contain days, months and years */
+    UNIT_DATE,      /**< the 3 dimensions contain days, months and years */
+    /* mass concentration */
+    UNIT_GPM3       /**< grams per cubic meters */
     /* extend this list as needed */
 };
 
diff --git a/sys/phydat/phydat_str.c b/sys/phydat/phydat_str.c
index 27916b31bea712c47591fc1bf23e60fba1d28bbd..f450c9aa65938d9944ee41c23b2d2938073cb3e2 100644
--- a/sys/phydat/phydat_str.c
+++ b/sys/phydat/phydat_str.c
@@ -102,6 +102,7 @@ const char *phydat_unit_to_str(uint8_t unit)
         case UNIT_PERCENT:  return "%";
         case UNIT_CTS:      return "cts";
         case UNIT_COULOMB:  return "C";
+        case UNIT_GPM3:     return "g/m^3";
         default:            return "";
     }
 }