diff --git a/piker/calc.py b/piker/calc.py
index 2e64c684..0f6d0e72 100644
--- a/piker/calc.py
+++ b/piker/calc.py
@@ -22,22 +22,28 @@ import itertools
 
 
 def humanize(number, digits=1):
-    """Convert large numbers to something with at most 3 digits and
+    '''Convert large numbers to something with at most ``digits`` and
     a letter suffix (eg. k: thousand, M: million, B: billion).
-    """
+
+    '''
     try:
         float(number)
     except ValueError:
         return 0
     if not number or number <= 0:
-        return number
+        return round(number, ndigits=digits)
+
     mag2suffix = {3: 'k', 6: 'M', 9: 'B'}
     mag = math.floor(math.log(number, 10))
     if mag < 3:
-        return number
+        return round(number, ndigits=digits)
+
     maxmag = max(itertools.takewhile(lambda key: mag >= key, mag2suffix))
-    return "{:.{digits}f}{}".format(
-        number/10**maxmag, mag2suffix[maxmag], digits=digits)
+
+    return "{value}{suffix}".format(
+        value=round(number/10**maxmag, ndigits=digits),
+        suffix=mag2suffix[maxmag],
+    )
 
 
 def percent_change(init, new):