This depends on the type of oil you are using.
If you have 25:1 ratio oil, it is 200ml per 5 litres or 40ml per litre. This applies to most oils you can purchase from hardware stores and department stores.
If you have 50:1 ratio oil, it is 100ml per 5 litres or 20ml per litre. This applies to the high quality oils available at your garden equipment specialists, and branded by manufacturers such as Husqvarna, Shindaiwa, Echo and Stihl
A rule of thumb tip.... if you are not sure, you are best to use a 25:1 ratio mix as you are far better to run your machine too rich than too lean.
If you do not use enough two stroke oil in your mix, you run the risk of serious and often permanent damage to your equipment.