diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index 94aaedd..cbed4cd 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -73,7 +73,9 @@ def pressure_height(pressure: float, surface: float=PRESSURE_MSL) -> float:
     Return the approximate altitude, in meters, for a given pressure in
     millibar.
     """
-    return (1 - (pressure / surface) ** 0.190284) * 145366.45 * 0.3107596
+    factor = 1.0195528177497388
+
+    return (1 - (pressure / surface) ** 0.190284) * 145366.45 * 0.3048 * factor
 
 def lapse(temp: float, delta: float, rate=LAPSE_RATE_DRY) -> float:
     """