Please advise if you can

I have one litre of liquid, this is equal to 1000 ml. I want to add 25% more liquid to the original volume.

I say 25% / 100 x 1000 = 250 ml. I then add this to the original 1000 ml to give 1250 ml, then I say; 1250 ml / 1000 ml = 1.25 L

The maths looks good, but the problem for me is in the units, you see if ml / ml is cancelled out, then I know its a fluid, but where does the L litre come from if I have cancelled the units out?

I thought that would leave unity?

David