How to choose the perfect length for a showreel
It depends on what your showreel is selling, a production company, or a role you can do (editor, director, producer, writer etc. )
It's an important tool in selling yourself or your production company through self-promotion in which a website by itself can't do. So its important to get it right, with this the length of a showreel is up to you in many ways but on average isn't longer than most songs by being 3 or 4 minutes long.
Yet it is important to look at the footage material you are using to create the showreel for, if you don't have 3 minutes of great footage material to use don't try and stretch it so your work doesn't look its best and loses the feeling that you have created in your project in roles such as editor, director, producer, writer etc.
If you worrying on the length of your showreel, you have the possibility of creating a short version of a minute, a minute can run a lot longer than you think and give a long more impact on your possible employer or interested party that could go onto suggesting you for work opportunities. If you feel you have enough footage material you could also make a 3-4 minute version. A showreel any longer than this can get boring for you possible employer to watch, its there time your wasting your showreel needs to be sharp and interesting. With a showreel that runs to long your possible employer might not bother watching it all the way through, so missing out on material 'gold' they could really want and were looking for in style and tone yet you placed it in the 4th of 5th minute of your showreel, yet employer have already switched off making them missing to give you a phone call or email for work opportunities.