This post describes how to adapt the size of the Grub splash screen and the virtual terminal on Debian.

In the following, I will set both to the size of 1280 x 1024 pixels. This may not suit your installation. To be sure, install the tool hwinfo and check the available configurations:

Grub splash scren

Open /etc/default/grub (as root) and add/modify the following lines:

Afterwards, update the grub configuration and reboot:

Now, the Grub splash screen appears larger, but the virtual console of Debian is still quite tiny.

Debian virtual console

For increasing the size of Debian’s virtual terminal, open /etc/default/grub, again and add the following line:

Further Reading

If this solution did not work for you, you may try other suggestions from this stackoverflow thread.