If you use standard baking potatoes around the same size as mine (or 4 medium russet potatoes), my baking times should be accurate. However, if you want to use this method for other sized potatoes, then the baking time will vary. To test if the potatoes are ready, you can test one with a skewer to see if it’s tender (only do this to one, though, as it can let out the steam and affect the fluffy center). Alternatively, using an oven mitt or kitchen towel, pick a potato up and lightly squeeze it to see if it is tender. Be careful not to burn your hands when doing this. If the potato isn’t soft, then place it back in the oven for a further 5+ minutes.