How long does it take to run a half marathon without specific training?

Most people without specific training take somewhere between 2h30m to 3h, but it really varies depending on your overall fitness level. What a lot of people don't account for is that the last 5km are brutal when you haven't trained for it - that's when your body really hits the wall. If you're someone who does irregular exercise (like the occasional run here and there), you might manage to get through in around 2h15m without suffering too much, but I wouldn't count on it. Leg pain and mental fatigue tend to be worse than the distance itself would suggest.

It's going to depend a lot on your overall cardiovascular fitness - people who already do some kind of activity can finish in 2h30m to 3h, but the real risk is you starting out way too fast in the first few kilometers because you're pumped up and then completely hitting the wall on the way back, which tanks your final time.

Without specific training it's tough, but you can do it if you have some base fitness. I know people who've done it in 2h45m or 3h, but it really depends on what you were already doing - if you've been walking, cycling or doing anything regularly, it gets a lot easier. If you're starting from zero, prepare yourself to suffer quite a bit from kilometer 15 onwards.

The big mistake is going out too fast at the start when you feel good and have energy. Then in the last 5-6 km your legs feel heavy as lead and the time drags out. Ideally you need at least a few months of prep with progressive runs so you don't burn yourself out halfway. Without that, expect something between 2h30m and 3h30m depending on your overall fitness level, but a lot will depend on how your body performs that day - humidity, heat, whether you ate well beforehand, all that stuff matters.