diff --git a/paddle/gserver/layers/ConvBaseLayer.cpp b/paddle/gserver/layers/ConvBaseLayer.cpp
index b9359867b9cceb334d1f870755b611004a467fa7..6bc3b3b801796a227a7b767c8da048a3ccf88827 100644
--- a/paddle/gserver/layers/ConvBaseLayer.cpp
+++ b/paddle/gserver/layers/ConvBaseLayer.cpp
@@ -14,6 +14,7 @@ limitations under the License. */
 
 #include "paddle/utils/Logging.h"
 #include "ConvBaseLayer.h"
+#include "paddle/math/MathUtils.h"
 namespace paddle {
 
 bool ConvBaseLayer::init(const LayerMap& layerMap,
@@ -95,18 +96,22 @@ size_t ConvBaseLayer::calOutputSize() {
          if (inW[i] == 0)
            inW[i] = config_.inputs(i).conv_conf().output_x();
          outH.push_back(
-             imageSize(inH[i], filterSizeY_[i], paddingY_[i], strideY_[i]));
+             imageSize(inH[i], filterSizeY_[i], paddingY_[i], strideY_[i],
+                       caffeMode_));
          outW.push_back(
-             imageSize(inW[i], filterSize_[i], padding_[i], stride_[i]));
+             imageSize(inW[i], filterSize_[i], padding_[i], stride_[i],
+                       caffeMode_));
        } else {
          if (inH[i] == 0)
            inH[i] = config_.inputs(i).conv_conf().img_size();
          if (inW[i] == 0)
            inW[i] = config_.inputs(i).conv_conf().img_size();
          outH.push_back(
-             outputSize(inH[i], filterSizeY_[i], paddingY_[i], strideY_[i]));
+             outputSize(inH[i], filterSizeY_[i], paddingY_[i], strideY_[i],
+                        caffeMode_));
          outW.push_back(
-             outputSize(inW[i], filterSize_[i], padding_[i], stride_[i]));
+             outputSize(inW[i], filterSize_[i], padding_[i], stride_[i],
+                        caffeMode_));
        }
        CHECK_EQ(outH[i], outH[0]);
        CHECK_EQ(outW[i], outW[0]);
diff --git a/paddle/gserver/layers/ConvBaseLayer.h b/paddle/gserver/layers/ConvBaseLayer.h
index 4d5b2b8d05af73c2a800ade7ff4717a150a2cd7b..b80cab899585e7bd93bfc86d8afa116d343d36d7 100644
--- a/paddle/gserver/layers/ConvBaseLayer.h
+++ b/paddle/gserver/layers/ConvBaseLayer.h
@@ -91,43 +91,6 @@ public:
   virtual size_t calOutputSize();
 
   Weight& getWeight(int idx) { return *weights_[idx]; }
-
-  /**
-   * Calculate output size based on caffeMode_.
-   * - input(+padding): 0123456789
-   * - imageSize(+padding) = 10;
-   * - filterSize = 3;
-   * - stride = 2;
-   * - caffeMode_ is true:
-       - output: (012), (234), (456), (678)
-       - outputSize = 4;
-   * - caffeMode_ is false:
-   *   - output: (012), (234), (456), (678), (9)
-   *   - outputSize = 5;
-   */
-  int outputSize(int imageSize, int filterSize, int padding, int stride) {
-    int outputSize;
-    if (!caffeMode_) {
-     outputSize =
-          (imageSize - filterSize + 2 * padding + stride - 1) / stride + 1;
-    } else {
-      outputSize = (imageSize - filterSize + 2 * padding) / stride + 1;
-    }
-    CHECK_GE(outputSize, 1);
-    return outputSize;
-  }
-
-  int imageSize(int outputSize, int filterSize, int padding, int stride) {
-    int imageSize;
-    if (!caffeMode_) {
-     imageSize =
-         (outputSize - 1) * stride + filterSize - 2 * padding - stride + 1;
-    } else {
-     imageSize = (outputSize - 1) * stride + filterSize - 2 * padding;
-    }
-    CHECK_GE(imageSize, 1);
-    return imageSize;
-  }
 };
 
 }  // namespace paddle
diff --git a/paddle/gserver/tests/test_ConvTrans.cpp b/paddle/gserver/tests/test_ConvTrans.cpp
index 9246484ba22c2966c80aa4605ee508e0e92a674a..bff7222b29907cb66d79decea76e1b5e26205ddf 100644
--- a/paddle/gserver/tests/test_ConvTrans.cpp
+++ b/paddle/gserver/tests/test_ConvTrans.cpp
@@ -20,6 +20,7 @@ limitations under the License. */
 #include "paddle/trainer/Trainer.h"
 #include "paddle/utils/GlobalConstants.h"
 #include "paddle/gserver/layers/ExpandConvTransLayer.h"
+#include "paddle/math/MathUtils.h"
 
 #include "TestUtil.h"
 #include "LayerGradUtil.h"
@@ -56,11 +57,9 @@ TEST(Layer, convTransLayerFwd) {
     conv->set_groups(1);
     conv->set_filter_channels(3 / conv->groups());
     conv->set_img_size(16);
-    conv->set_output_x(
-        (2 * conv->padding() + conv->img_size() - conv->filter_size()) /
-            ((float)conv->stride()) +
-        1.5);
-
+    conv->set_output_x(outputSize(conv->img_size(), conv->filter_size(),
+                                  conv->padding(), conv->stride(),
+                                  /* caffeMode */ true));
     configt.layerConfig.set_size(conv->img_size() * conv->img_size() *
                                 configt.layerConfig.num_filters());
     configt.layerConfig.set_name("convTrans");
@@ -99,10 +98,9 @@ TEST(Layer, convTransLayerFwd) {
     conv->set_groups(1);
     conv->set_filter_channels(conv->channels() / conv->groups());
     conv->set_img_size(16);
-    conv->set_output_x(
-        (2 * conv->padding() + conv->img_size() - conv->filter_size()) /
-            ((float)conv->stride()) +
-        1.5);
+    conv->set_output_x(outputSize(conv->img_size(), conv->filter_size(),
+                                  conv->padding(), conv->stride(),
+                                  /* caffeMode */ true));
     config.layerConfig.set_size(conv->output_x() * conv->output_x() *
                                 config.layerConfig.num_filters());
     config.layerConfig.set_name("conv");
diff --git a/paddle/gserver/tests/test_LayerGrad.cpp b/paddle/gserver/tests/test_LayerGrad.cpp
index 0fed97a73b0a4dcba973fdbad4eb9e6bb99d9e05..02a30719f98e09a109f3d367af5250af29fc87ec 100644
--- a/paddle/gserver/tests/test_LayerGrad.cpp
+++ b/paddle/gserver/tests/test_LayerGrad.cpp
@@ -336,10 +336,9 @@ void testConvTransLayer(const string& type, bool trans, bool useGpu) {
   conv->set_groups(1);
   conv->set_filter_channels(3 / conv->groups());
   conv->set_img_size(16);
-  conv->set_output_x(
-      (2 * conv->padding() + conv->img_size() - conv->filter_size()) /
-          ((float)conv->stride()) +
-      1.5);
+  conv->set_output_x(outputSize(conv->img_size(), conv->filter_size(),
+                                conv->padding(), conv->stride(),
+                                /* caffeMode */ true));
 
   config.layerConfig.set_size(conv->img_size() * conv->img_size() *
                               config.layerConfig.num_filters());
diff --git a/paddle/math/MathUtils.cpp b/paddle/math/MathUtils.cpp
index c1af8628d03c50185089b45f3a0502726da9137e..548f17936381c7e1c4d0c2c9661b197f3f06bd35 100644
--- a/paddle/math/MathUtils.cpp
+++ b/paddle/math/MathUtils.cpp
@@ -80,4 +80,17 @@ int outputSize(int imageSize, int filterSize, int padding, int stride,
   return outputSize;
 }
 
+int imageSize(int outputSize, int filterSize, int padding, int stride,
+              bool caffeMode) {
+  int imageSize;
+  if (!caffeMode) {
+   imageSize =
+       (outputSize - 1) * stride + filterSize - 2 * padding - stride + 1;
+  } else {
+   imageSize = (outputSize - 1) * stride + filterSize - 2 * padding;
+  }
+  CHECK_GE(imageSize, 1);
+  return imageSize;
+}
+
 }  // namespace paddle
diff --git a/paddle/math/MathUtils.h b/paddle/math/MathUtils.h
index 49d0c10a8f5e4dcdaf22dca77a3f113400b16646..ae035e55bcceb2efb9ef5405f4c982ed280386a5 100644
--- a/paddle/math/MathUtils.h
+++ b/paddle/math/MathUtils.h
@@ -60,4 +60,7 @@ void sparseRand(int* major, int* minor, int nnz, int majorLen, int minorMax,
 int outputSize(int imageSize, int filterSize, int padding, int stride,
                bool caffeMode);
 
+int imageSize(int outputSize, int filterSize, int padding, int stride,
+              bool caffeMode);
+
 }  // namespace paddle
diff --git a/python/paddle/trainer/config_parser.py b/python/paddle/trainer/config_parser.py
index b75c2618411d30459d460d0683e8113c05d857bf..8b13e4a14254458ca6cbe1b610ff5a6504c17dac 100644
--- a/python/paddle/trainer/config_parser.py
+++ b/python/paddle/trainer/config_parser.py
@@ -1107,14 +1107,10 @@ def parse_conv(conv, input_layer_name, conv_conf, trans=False):
                       ("Input layer %s: Incorrect input image size %d for input "
                        + "image pixels %d")
                       % (input_layer_name, conv_conf.img_size, img_pixels))
-        if conv.caffe_mode:
-            conv_conf.output_x = \
-                1 + int(math.floor((2 * conv.padding + conv_conf.img_size \
-                - conv.filter_size) / float(conv.stride)))
-        else:
-            conv_conf.output_x = \
-                1 + int(math.ceil((2 * conv.padding + conv_conf.img_size \
-                - conv.filter_size) / float(conv.stride)))
+                
+        conv_conf.output_x = cnn_output_size(
+            conv_conf.img_size, conv_conf.filter_size, 
+            conv_conf.padding, conv_conf.stride, conv_conf.caffe_mode)
     else:
         outputSize = g_layer_map[input_layer_name].size / conv.channels
         print('channels=%d size=%d'%(conv.channels,