As a few have said the link between weight gain and calories in alcohol is a little bit of a red herring (and therefore the newsbeat calculator is pretty much bollocks all use!).
This is because alcohol doesn't convert to anything that the body can store so you aren't 'laying it down as fat' like some people might have you believe.
The problem lies with eating in combination with drinking. For starters alcohol stimulates your appetite which causes you to eat more and secondly it strongly inhibits the metabolism of fat and carbohydrate.
I understand that studies have shown drinkers can actually lose weight if they replace carbs with alcohol and can avoid eating (particularly fatty foods) around the time of drinking.
Actually, thinking about all the above, the newsbeat calculator is worse than bollocks because it makes a direct connection between food that is terrible for you and alcohol - I could see people thinking if they cut down on their drink this calculator will tell them what they could eat as a reward!
Apologies in advance for repeating any info already posted or not proven by SCIENCE!