diff --git a/README.rst b/README.rst
index 46d7123..e74d3e6 100644
--- a/README.rst
+++ b/README.rst
@@ -18,4 +18,4 @@ Using histograms in other pages
 You can use the built-in ``histogram_for`` template tag::
 
     {% load histograms %}
-    {% histogram_for 'appname.Model' 'histogram_field' %}
+    {% histogram_for appname.Model 'histogram_field' 1 1 %}
diff --git a/django_histograms/templates/histograms/report.html b/django_histograms/templates/histograms/report.html
index 6aa60c4..bc7f167 100644
--- a/django_histograms/templates/histograms/report.html
+++ b/django_histograms/templates/histograms/report.html
@@ -20,7 +20,7 @@ <h2 style="padding-top: 1em;">{{ label }} ({{ count }})</h2>
                         {% if day_labels %}
                             <span class="label">{{ forloop.counter }}</span>
                         {% endif %}
-                        <span class="count" style="height: {% widthratio num total 100 %}%">
+                        <span class="count" style="height: {% widthratio num total ratio %}%">
                             ({{ num }})
                         </span>
                     </a>
diff --git a/django_histograms/templatetags/histograms.py b/django_histograms/templatetags/histograms.py
index a200267..4dde26a 100644
--- a/django_histograms/templatetags/histograms.py
+++ b/django_histograms/templatetags/histograms.py
@@ -10,10 +10,10 @@
 
 
 @tag(register, [Model(), Variable(), Optional([Variable(), Variable()])])
-def histogram_for(model, attname, months=2, day_labels=True):
+def histogram_for(context, model, attname, months=2, day_labels=True):
     return Histogram(model, attname, months=months).render(css=True, day_labels=day_labels)
 
 
 @tag(register, [Model(), Variable(), Optional([Variable(), Variable()])])
-def histogram_for_days(model, attname, days=31, day_labels=True):
+def histogram_for_days(context, model, attname, days=31, day_labels=True):
     return Histogram(model, attname, days=days).render(css=True, day_labels=day_labels)
diff --git a/django_histograms/utils.py b/django_histograms/utils.py
index 6f06dee..e88e8d1 100644
--- a/django_histograms/utils.py
+++ b/django_histograms/utils.py
@@ -64,7 +64,7 @@ def __init__(self, model, attname, queryset=None, months=None, days=None):
         self.model = model
         self.attname = attname
         self._queryset = None
-        assert(months or days, 'You must pass either months or days, not both.')
+        assert months or days, 'You must pass either months or days, not both.'
         self.months = months
         self.days = days
     
@@ -104,14 +104,22 @@ def get_report(self):
             
         qs = self.get_query_set().values(self.attname).annotate(
             num=Count("pk")
-        ).filter(**{"%s__gt" % self.attname: cutoff})
+        ).filter(**{"%s__gt" % str(self.attname): cutoff})
         
         for data in qs.iterator():
             idx = grouper(data[self.attname])
             months[idx][1][day_grouper(data[self.attname])] += data["num"]
             months[idx][2] += data["num"]
-        print months
+
+        total = sum(o for m in months.itervalues() for o in m[1])
+        max_num = max(o for m in months.itervalues() for o in m[1])
+        if not (total and max_num):
+            ratio = 0
+        else:
+            ratio = total / max_num * 100
+
         return {
             "results": months.values(),
-            "total": sum(o for m in months.itervalues() for o in m[1]),
+            "total": total,
+            "ratio": ratio
         }