Thank you for sharing your question about painting your stairs. Doing some general addition of the area of your stairs we should be able to determine how much paint you'll need. If each step for example is 900mm wide and 300mm deep, putting 3 steps together would give you a 900mm x 900mm square. Add the next three steps would give you 1800mm x 900mm, add the last two and you would have a total of 2400mm x 900mm. If we multiply 2400mm x 900mm it would give us an area of 2.16sq meters. Add the landing of 1sq meter and you will have an overall area of 3.16sq meters.
If we had to do two coats of stain or paint over the stair we would need twice the area. So 2.16sq meters x 2 equals 4.32sq meters. Generally speaking, a litre of paint will cover an area of anywhere from 12 to 14sq meters. Professional painters can sometimes extend this out to 16sq meters.
The best thing to do is to look at the coverage area at the back of the can. This will show you the amount of area a single litre of paint will cover. The same goes for paint and varnish. I've placed an example for you to see. The measurements I've placed are for reference only. Please adjust the to your requirements.
Please keep us updated with your progress, we look forward to seeing your stairs painted and ready for use.
If you need further assistance, please let us know.