Expected tip for driver of rented car in Sri Lanka

Question

I traveled around Sri Lanka in a rented car with driver.
The contract has this note:

Above Price Not includes
Driver Tip - We encourage our customers , whenever they wish, to offer drivers tips for satisfactory services. Tipping drivers is accepted practice, and it is especially beneficial on long tours when drivers may be away from home for long periods

• About the driver, the contract only explicitly cites "Driver Meals and lodging" as included.
• I am not particularly demanding, but I am perfectly happy with the service.
• Coming from a no-tips country, I have no remote idea what the driver is used to receiving.

Is there a rule of thumb for this kind of tip?
For instance a percentage of the sum paid to the driver's employer? (USD 250 for 5 days)

Answer 1

We did this earlier this year. We had a driver for 7 days. The overall cost including railway tickets was 73000 rupees (~350 Euros). Food and lodging for the driver was included as well.

At the end we gave the driver 5000 rupees (~25 Euros) as tip. He was very happy with it, especially since he had told us before that he earns 1500 rupees (~7.50 Euros) a day. This also demonstrates that the company he works for earns a lot! I would assume this to be the general rule.

Answer 2

I can not say if this amount will be shared by driver and company or the driver alone. If this fess is all for the driver, then it seems quite good and reasonable (factor in fuel cost separately). However, if fees is shared, feel free to give an amount that you think is just/deserving and also be aware of the difference in value of different currencies.