diff --git a/rattail/pricing.py b/rattail/pricing.py
index 2ddfdd71..0bb4281a 100644
--- a/rattail/pricing.py
+++ b/rattail/pricing.py
@@ -27,6 +27,7 @@ Pricing Utilities
 from __future__ import unicode_literals, absolute_import
 
 import decimal
+import warnings
 
 
 def gross_margin(price, cost, percentage=False):
@@ -59,12 +60,19 @@ def gross_margin(price, cost, percentage=False):
     return 100 * margin
 
 
-def calculate_markup(margin):
+def calculate_markup_from_margin(margin, from_decimal=False):
     """
     Calculate the "markup" value corresponding to the given margin.
 
-    :param margin: Profit margin as decimal percentage (e.g. between
-       0.0 and 1.0).
+    This assumes the ``margin`` value is user-friendly, e.g. ``37.5``
+    instead of ``0.375`` to represent 37.5%, unless ``from_decimal``
+    is true in which case the decimal format is assumed.
+
+    :param margin: Profit margin percentage.
+
+    :param from_decimal: If false (the default), then ``margin``
+       should (normally) be between 0 - 100.  But if true, then
+       ``margin`` is assumed to be between 0.0 and 1.0 instead.
 
     :returns: Equivalent cost markup as decimal value (e.g. 1.4).
     """
@@ -73,7 +81,24 @@ def calculate_markup(margin):
     if margin == 0:
         return 1
 
-    return 1 / (1 - margin)
+    if from_decimal:
+        margin *= 100
+
+    return 100 / (100 - margin)
+
+
+def calculate_markup_from_margin_decimal(margin):
+    warnings.warn("calculate_markup_from_margin_decimal() is deprecated; "
+                  "please use calculate_markup_from_margin() instead",
+                  DeprecationWarning, stacklevel=2)
+    return calculate_markup_from_margin(margin, from_decimal=True)
+
+
+def calculate_markup(margin):
+    warnings.warn("calculate_markup() is deprecated; please use "
+                  "calculate_markup_from_margin() instead",
+                  DeprecationWarning, stacklevel=2)
+    return calculate_markup_from_margin(margin, from_decimal=True)
 
 
 def calculate_variance(oldvalue, newvalue):