Confused about tipping on board a cruise ship? Below is a detailed guide on what you can expect on board some of the world's biggest cruise lines.

Before we go on with the numbers though, there are a couple of concepts you need to be aware of. There are three ways a cruise line can charge tips and these are as follows:

• Automatic - a certain amount is automatically added to your onboard account and this is per person per day. The amount will depend on the cabin category you are staying at. Some cruise lines, like Carnival will exclude children from this. Most cruise lines will also allow you to adjust this amount in either direction - please see the Guest Services Desk for this. A further 15-20% is added on top of all bar bills, specialty dining cover charges and spa fees. These are usually non-negotiable.

• Included - this is the case on board the all-inclusive cruise lines, like Silversea, etc. Alternatively, book your cruise on an all-inclsive fare, like the Princess Plus Fare that includes gratuities alongside other extras. Cruise lines like Royal Caribbean let guests pre-pay their gratuities prior to boarding the cruise.

• Optional - out of the cruise lines below, P&O Australia is the only one that does not charge guests gratuities, not even on the bar bills and specialty dining. You are welcome to tip a member of staff for extraordinary service if you like and can do so by handing them cash or asking the service desk to add it to your onboard account.