# How do I find output size of a network?

The input to a convolutional layer of a neural network is an image of size $$128\times 128\times 3.$$

$$40$$ convolutional filters of size $$5\times 5$$ are applied to it. Would you get an output? If no then why not? If yes, what will be the output size?

Yes, and it would be $$124 \times 124 \times40$$.
$$(dim_x - filterdim_x + 1) \times (dim_y - filterdim_y + 1) \times filters$$
$$(128 - 5 + 1) \times (128 - 5 + 1) \times 40 = 124 \times 124 \times40$$