Here’s the recommended permissions for WordPress.

Permissions

Directories = 755
Files = 644

Install From Scratch

If you’re starting from scratch, follow the instructions below.

Assuming you’re logged in as normal user. Use sudo to execute commands as superuser.

cd /var/www/
sudo wget https://wordpress.org/latest.tar.gz
sudo tar -xzvf latest.tar.gz
sudo chown -R www-data:www-data wordpress

Fix Current

If your permissions are wrong, then perform the following.

sudo find /var/www/wordpress/ -type d -exec chmod 755 {} \
sudo find /var/www/wordpress/ -type f -exec chmod 644 {} \