Yes, classifier networks using fc layers don’t work on variable sized images. This is generally true regardless the framework. The most commonly used option is to simply resize the test images to be similar to train images. On a slightly related note, you can use even fancier methods like 5-crop to enhance your test score. http://pytorch.org/docs/master/torchvision/transforms.html#torchvision.transforms.FiveCrop 21