diff --git a/lib/mini_paperclip/validators/file_size_validator.rb b/lib/mini_paperclip/validators/file_size_validator.rb
index 944fce0..ae75eed 100644
--- a/lib/mini_paperclip/validators/file_size_validator.rb
+++ b/lib/mini_paperclip/validators/file_size_validator.rb
@@ -14,8 +14,32 @@ def validate_each(record, attribute, value)
               record.errors.add(attachment_file_size_name, :less_than, count: count)
             end
           end
+
+          if check_value = options[:greater_than]
+            unless attachment_file_size > check_value
+              count = ActiveSupport::NumberHelper.number_to_human_size(check_value)
+              record.errors.add(attribute, :greater_than, count: count)
+              record.errors.add(attachment_file_size_name, :greater_than, count: count)
+            end
+          end
+
+          if check_value = (options[:within] || options[:in])
+            unless check_value.include?(attachment_file_size)
+              record.errors.add(attribute, :within, count: formatted_range(check_value))
+              record.errors.add(attachment_file_size_name, :within, count: formatted_range(check_value))
+            end
+          end
         end
       end
+
+      private
+
+      def formatted_range(range)
+        dots = range.exclude_end? ? "..." : ".."
+        first = ActiveSupport::NumberHelper.number_to_human_size(range.begin)
+        last = ActiveSupport::NumberHelper.number_to_human_size(range.last)
+        "#{first}#{dots}#{last}"
+      end
     end
   end
 end
diff --git a/spec/mini_paperclip/validators/file_size_validator_spec.rb b/spec/mini_paperclip/validators/file_size_validator_spec.rb
index 04597f6..5352385 100644
--- a/spec/mini_paperclip/validators/file_size_validator_spec.rb
+++ b/spec/mini_paperclip/validators/file_size_validator_spec.rb
@@ -1,28 +1,135 @@
 RSpec.describe MiniPaperclip::Validators::FileSizeValidator do
-  it "#validate_each with valid file size" do
-    validator = MiniPaperclip::Validators::FileSizeValidator.new(
-      attributes: :img,
-      less_than: 1.megabytes,
-    )
-    mock = double('Record')
-    attachment = double('Attachment')
-    allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(1.kilobytes)
-    expect(mock).to_not receive(:errors)
-    validator.validate_each(mock, :img, attachment)
+  describe "less_than" do
+    it "#validate_each with valid file size" do
+      validator = MiniPaperclip::Validators::FileSizeValidator.new(
+        attributes: :img,
+        less_than: 1.megabytes,
+      )
+      mock = double('Record')
+      attachment = double('Attachment')
+      allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(1.kilobytes)
+      expect(mock).to_not receive(:errors)
+      validator.validate_each(mock, :img, attachment)
+    end
+
+    it "#validate_each with invalid file size" do
+      validator = MiniPaperclip::Validators::FileSizeValidator.new(
+        attributes: :img,
+        less_than: 1.megabytes,
+      )
+      mock = double('Record')
+      attachment = double('Attachment')
+      allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(2.megabytes)
+      errors_mock = double('Errors')
+      allow(mock).to receive(:errors).and_return(errors_mock)
+      expect(errors_mock).to receive(:add).with(:img, :less_than, { count: "1 MB" })
+      expect(errors_mock).to receive(:add).with("img_file_size", :less_than, { count: "1 MB" })
+      validator.validate_each(mock, :img, attachment)
+    end
+  end
+
+  describe "greater_than" do
+    it "#validate_each with valid file size" do
+      validator = MiniPaperclip::Validators::FileSizeValidator.new(
+        attributes: :img,
+        greater_than: 1.megabytes,
+      )
+      mock = double('Record')
+      attachment = double('Attachment')
+      allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(2.megabytes)
+      expect(mock).to_not receive(:errors)
+      validator.validate_each(mock, :img, attachment)
+    end
+
+    it "#validate_each with invalid file size" do
+      validator = MiniPaperclip::Validators::FileSizeValidator.new(
+        attributes: :img,
+        greater_than: 1.megabytes,
+      )
+      mock = double('Record')
+      attachment = double('Attachment')
+      allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(1.kilobytes)
+      errors_mock = double('Errors')
+      allow(mock).to receive(:errors).and_return(errors_mock)
+      expect(errors_mock).to receive(:add).with(:img, :greater_than, { count: "1 MB" })
+      expect(errors_mock).to receive(:add).with("img_file_size", :greater_than, { count: "1 MB" })
+      validator.validate_each(mock, :img, attachment)
+    end
+  end
+
+  describe "within (1.megabytes..2.megabytes)" do
+    let(:validator) do
+      validator = MiniPaperclip::Validators::FileSizeValidator.new(
+        attributes: :img,
+        within: 1.megabytes..2.megabytes,
+      )
+    end
+
+    context "valid case" do
+      [1.megabytes, 1.5.megabytes, 2.megabytes].each do |file_size|
+        it "returns no error when file size is #{file_size}" do
+          mock = double('Record')
+          attachment = double('Attachment')
+          allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(file_size)
+          expect(mock).to_not receive(:errors)
+          validator.validate_each(mock, :img, attachment)
+        end
+      end
+    end
+
+    context "too large (2.megabytes + 1)" do
+      it "returns error" do
+        mock = double('Record')
+        attachment = double('Attachment')
+        allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(2.megabytes + 1)
+        errors_mock = double('Errors')
+        allow(mock).to receive(:errors).and_return(errors_mock)
+        expect(errors_mock).to receive(:add).with(:img, :within, { count: "1 MB..2 MB" })
+        expect(errors_mock).to receive(:add).with("img_file_size", :within, { count: "1 MB..2 MB" })
+        validator.validate_each(mock, :img, attachment)
+      end
+    end
+
+    context "too small (1.megabytes - 1)" do
+      it "returns error" do
+        mock = double('Record')
+        attachment = double('Attachment')
+        allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(1.megabytes - 1)
+        errors_mock = double('Errors')
+        allow(mock).to receive(:errors).and_return(errors_mock)
+        expect(errors_mock).to receive(:add).with(:img, :within, { count: "1 MB..2 MB" })
+        expect(errors_mock).to receive(:add).with("img_file_size", :within, { count: "1 MB..2 MB" })
+        validator.validate_each(mock, :img, attachment)
+      end
+    end
   end
 
-  it "#validate_each with invalid file size" do
-    validator = MiniPaperclip::Validators::FileSizeValidator.new(
-      attributes: :img,
-      less_than: 1.megabytes,
-    )
-    mock = double('Record')
-    attachment = double('Attachment')
-    allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(2.megabytes)
-    errors_mock = double('Errors')
-    allow(mock).to receive(:errors).and_return(errors_mock)
-    expect(errors_mock).to receive(:add).with(:img, :less_than, { count: "1 MB" })
-    expect(errors_mock).to receive(:add).with("img_file_size", :less_than, { count: "1 MB" })
-    validator.validate_each(mock, :img, attachment)
+  describe "alias 'in' (1.megabytes...3.megabytes)" do
+    let(:validator) do
+      validator = MiniPaperclip::Validators::FileSizeValidator.new(
+        attributes: :img,
+        in: 1.megabytes...3.megabytes,
+      )
+    end
+    [1.megabytes, 1.5.megabytes, 3.megabytes - 1 ].each do |file_size|
+      it "returns no error when file size is #{file_size}" do
+        mock = double('Record')
+        attachment = double('Attachment')
+        allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(file_size)
+        expect(mock).to_not receive(:errors)
+        validator.validate_each(mock, :img, attachment)
+      end
+    end
+
+    it "returns error when file size is 3.megebaytes" do
+      mock = double('Record')
+      attachment = double('Attachment')
+      allow(mock).to receive(:read_attribute_for_validation).with('img_file_size').and_return(3.megabytes)
+      errors_mock = double('Errors')
+      allow(mock).to receive(:errors).and_return(errors_mock)
+      expect(errors_mock).to receive(:add).with(:img, :within, { count: "1 MB...3 MB" })
+      expect(errors_mock).to receive(:add).with("img_file_size", :within, { count: "1 MB...3 MB" })
+      validator.validate_each(mock, :img, attachment)
+    end
   end
 end