diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index 07b6660..b48bbe9 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -12,14 +12,15 @@ def kelvin(c: float) -> float:
 
 def vapor_pressure(dewpoint: float) -> float:
     """
-    Return the pressure of vapor in a parcel of a given dewpoint.
+    Return the pressure, in millibar, of vapor in a parcel of a given
+    dewpoint.
     """
     return 6.11 * 10 ** ((7.5 * dewpoint) / (237.3 + dewpoint))
 
 def saturated_vapor_pressure(temp: float) -> float:
     """
-    Return the pressure at which the vapor and condensation of a parcel of a
-    given temperature are at equilibrium.
+    Return the pressure, in millbar, at which the vapor and condensation of a
+    parcel of a given temperature are at equilibrium.
     """
     return 6.11 * 10 ** ((7.5 * temp) / (237.3 + temp))