You know the drill – you’re coming home after a night out and you have a sensible €20 stashed in your handbag to pay for your taxi. But there’s just one problem. Your journey (which should only cost about €20 anyway) costs a lot more.

We’ve all been there. There is some good news though, as a Dublin man has just developed a new app that calculates how much the cost should be based on the distance travelled. So basically, you’ll be able to see if you’re being charged fairly.

The Irish Daily Mail reports that Kevin Fagan came up with the idea after his English-born wife was bought on the “scenic-route” during certain journeys.

After one particularly expensive trip, Mr Fagan, a software engineer sat down and created Taxi Fair – an app that can help passengers see how much they should be charged for a journey.

All you have to do is download the app and hit start as soon as the taxi begins to move. Hit stop when the taxi stops and it will calculate your “fair” fare.

“It knows the complete tariff setting for the whole of Ireland, the standard fare, the day and the time, and it takes all that into consideration,” said Mr Fagan.

“At the end of the journey, it shows you a map of the route taken, so you can then verify that you haven’t been taken out of your way,” he added.

Mr Fagan said that the purpose of the app is to offer passengers peace of mind, and to allow them to see if they are being overcharged for a certain journey.

The app can be downloaded from the iTunes store for the fair price of 79cent.

What do you think? Good idea or bad idea?