One of the most frequently asked questions, usually asked by beginners is; how much time will it take me to build muscle ? However, the answer isn't as simple as the question itself. It takes into account, what is your starting point, what's the end goal and most importantly how good are your genes. So is there no accurate way of predicting the time needed to change your body ? Yes, but we can make assumptions and give an estimated time for everyone using these 3 factors;
The first factor, to predict the time needed for putting on muscle would be 'how hard you work';
This should come as no surprise. If you aren't working hard enough, taking too much rest, talking around in the gym or using your phone while working out you aren't going to grow. So optimize your work out with shorter rests, progressive overloads. However, don't work too hard, you may end up over training. Also lift the heaviest weight possible but keep in mind your form should stay correct. Don't spend anymore than an hour in the gym. So for quicker muscle gain work hard, correct and quick. Like Jason Statham said "Get Serious. Do 40 hard minutes.. Not an hour and a half of nonsense." Here's a workout routine that has everything figured out for you.
Secondly, it very well depends on your diet
Another unsurprising but overlooked fact is how good your diet is. If you are breaking down muscle but not giving it the right products for repair, you wont see any growth. Hence putting in the right foods to build muscle is probably even more important than the workout itself. The food you eat also acts as fuel and energy for the workout. Which means, if you're want to the first factor is dependent on your diet also. All the more reason to eat appropriately.
The third and equally important factor is; SLEEP
I can't stress this enough, if you're not sleeping then you wont grow. It's that simple. Your body recovers when you sleep. Your body grows when you recover. Which means Gains = Sleep. Sleep at least 7-9 hours at night for optimal muscle gain. Moreover, make sure you sleep for 7-9 hours straight. It isn't right to sleep for 5 hours and then 4 hours later in the day. Not only is this not a productive habit but it doesn't allow your body recover well. Hence make sure you rest well and have nice sleep every night consistently to gain muscle in less time.
How quick you gain muscle also depends on if you have worked out before or not. People who have worked out before gain muscle quicker than most beginners because of muscle memory. However, if you are a beginner and have started lifting, no matter how bad your genetics are, you will see considerable gains in a matter of a few weeks. These gains come quick and are known as newbie gains but as you stay consistent growth does plateau and will depend on how well and consistently you follow the fore mentioned factors. Stay Aesthetic and Stay healthy.