1 On average, the costs of carpet stretching will vary between $25-$100 per room. 2  For the whole house, it should cost around $200. 3  To get an exact quote for your particular job, consider getting multiple quotes for free from free services such as HomeAdvisor.com. For the whole house, it should cost around $200. 2  To get an exact quote for your particular job, consider getting multiple quotes for free from free services such as HomeAdvisor.com. 3  TheCarpets.net claim that you should be prepared to budget about $50 to $100 for the average room.