How many drinks do you need to justify a drinks package?

Divide the package's price a day by what you'd pay for an average drink. A $75-a-day package with $13 drinks breaks even at 5.8, so you need 6 drinks a day, or 41 drinks over a 7-day cruise, before it saves you money.

It's worth it if you'd have more drinks than its break-even number across the whole cruise, port days included, since lines usually charge the package for every day of the sailing. If you'd have fewer, buying drinks one at a time costs less. Within half a drink a day of break-even, the package buys convenience more than savings.

On the lines we track, a glass of house wine runs from about $4.48 on Star Clippers to about $16.25 on Hurtigruten, before any service charge. Many luxury and river lines include wine in the fare. Pick a line in the calculator to start from its price.

Count them if the package covers them and you'd otherwise pay for them. A specialty coffee or a bottle of water you'd skip without a package isn't a saving.

Not if you enter both prices the same way. Lines that add a service charge usually add it to drinks bought one at a time as well as to the package, so it raises both by the same share and the break-even number of drinks stays the same.

On many lines, yes: if one adult in a cabin buys an alcohol package, every adult in it must buy one too. Check your line's terms before you buy, and run the numbers for the lightest drinker in the cabin.

Yes, for free. Open "Embed this calculator on your site" under the calculator and paste the code into your page. It sizes itself to fit, and adding ?theme=dark to the frame address suits a dark site.