diff --git a/actionpack/lib/action_view/helpers/number_helper.rb b/actionpack/lib/action_view/helpers/number_helper.rb
index 98df5c169b..d1c8064c1b 100644
--- a/actionpack/lib/action_view/helpers/number_helper.rb
+++ b/actionpack/lib/action_view/helpers/number_helper.rb
@@ -260,7 +260,7 @@ module ActionView
           if number == 0
             digits, rounded_number = 1, 0
           else
-            digits = (Math.log10(number) + 1).floor
+            digits = (Math.log10(number.abs) + 1).floor
             rounded_number = BigDecimal.new((number / 10 ** (digits - precision)).to_s).round.to_f * 10 ** (digits - precision)
           end
           precision = precision - digits
@@ -459,7 +459,7 @@ module ActionView
           raise ArgumentError, ":units must be a Hash or String translation scope."
         end.keys.map{|e_name| DECIMAL_UNITS.invert[e_name] }.sort_by{|e| -e}
 
-        number_exponent = number != 0 ? Math.log10(number).floor : 0
+        number_exponent = number != 0 ? Math.log10(number.abs).floor : 0
         display_exponent = unit_exponents.find{|e| number_exponent >= e }
         number  /= 10 ** display_exponent
 
diff --git a/actionpack/test/template/number_helper_test.rb b/actionpack/test/template/number_helper_test.rb
index 31461e1833..c14dfb250f 100644
--- a/actionpack/test/template/number_helper_test.rb
+++ b/actionpack/test/template/number_helper_test.rb
@@ -83,6 +83,7 @@ class NumberHelperTest < ActionView::TestCase
   end
 
   def test_number_with_precision
+    assert_equal("-111.235", number_with_precision(-111.2346))
     assert_equal("111.235", number_with_precision(111.2346))
     assert_equal("31.83", number_with_precision(31.825, :precision => 2))
     assert_equal("111.23", number_with_precision(111.2346, :precision => 2))
@@ -184,6 +185,7 @@ class NumberHelperTest < ActionView::TestCase
   end
 
   def test_number_to_human
+    assert_equal '-123', number_to_human(-123)
     assert_equal '0', number_to_human(0)
     assert_equal '123', number_to_human(123)
     assert_equal '1.23 Thousand', number_to_human(1234)