The main curry ingredient that gives its “heat” is chilli.
And, generally speaking, the more chilli you put into a curry, the hotter it becomes.
There are several ways that chilli gets into curries – as chopped fresh chilli, chilli powder and curry powder (curry powder contains chilli).
Having read these articles, you’ll see that the type of chilli also affects the heat level.
Now we’re not going to get into a debate about whether you should use fresh chilli, chilli powder or curry powder – that is your choice.
The trick is to settle on one type of chilli, or brand of chilli powder or curry powder (you don’t usually know what types of chilli are in these products but most producers try to keep their products consistent).
If you use fresh chillies, you need to decide whether to use the seeds as well as the flesh of the fresh chillies.
Once you’ve chosen your chilli (with or without seeds), chilli powder or curry powder then it’s a matter of quantity.
If you make a curry using just one chilli and the curry is mild then it’s a certainty that following the same recipe but using 2 chillies will result in a hotter curry – using 3 chillies will be hotter still.
And if you follow a recipe and the result is too hot for your palate, then using less chilli will make it milder.
It’s all down to personal taste and experimentation.
And you need to be sensible about the curry heat. If you like hot curries but are cooking for somebody that likes only mild curries, you need to tone down the heat or cook 2 separate curries with different heat levels.
There’s a great article that you can read about how to cool down a curry that’s too hot.
If you’re holding a curry dinner party, you can make a few small curry dishes with a range of heat levels so people can find something that they really enjoy.
Here’s one last word advice. If you’re guessing about how much chilli to put into a curry, then err on the low side because nobody is going to enjoy a curry that is too hot.