diff --git a/src/nnet3/convolution.cc b/src/nnet3/convolution.cc
index 287ab7f47dd..1c5396949f8 100644
--- a/src/nnet3/convolution.cc
+++ b/src/nnet3/convolution.cc
@@ -976,7 +976,7 @@ static void ComputeTempMatrixSize(const ConvolutionComputationOptions &opts,
     // work out how many rows the temporary matrix should have, taking
     // into account the specified memory limit.
     temp_rows = computation->num_t_out * computation->num_images;
-    BaseFloat num_megabytes = (4 * temp_rows * temp_cols) / 1000000.0,
+    BaseFloat num_megabytes = (4 * (temp_rows / 1000.0) * (temp_cols / 1000.0)),
         megabyte_limit = opts.max_memory_mb;
     // C++ rounds down; here, we want to round up so we add one.
     int32 ratio = 1.0 + num_megabytes / megabyte_limit;
@@ -986,7 +986,7 @@ static void ComputeTempMatrixSize(const ConvolutionComputationOptions &opts,
     // >= temp_rows so that we don't have a small leftover piece.
     int32 new_num_t_out = (computation->num_t_out + ratio - 1) / ratio;
     temp_rows = new_num_t_out * computation->num_images;
-    BaseFloat new_num_megabytes = (4 * temp_rows * temp_cols) / 1000000.0;
+    BaseFloat new_num_megabytes = (4 * (temp_rows / 1000.0) * (temp_cols / 1000.0));
     // make sure we're within the memory limit.
     if (new_num_megabytes > 1.01 * megabyte_limit) {
       KALDI_WARN << "Memory consumed in convolution is more than requested "