A bulk should end when you no longer have visible ABS, once your abs have completely vanished it's time to go on a cut. So look at yourself in the mirror and make an assessment of how lean you are. If your abs not there, or are just barely visible, then diet yourself down first. Are you lean with abs and can see some veins here and there? If so then go on a bulk!
When your body fat is high you tend to gain more fat and less muscle. A lean physique is insulin sensitive and will prioritize muscle over fat gain given that your diet and training is in order.
if we're not talking specifically about physique related goals and your goals might be more strength related then I can see bulking to a little higher body fat so you can prioritize having better leverages and more food to fuel the strength gains. Mass moves Mass regardless of whether it's fat or muscle. Gaining weight while lifting weights will always make you stronger. But if your goal is to look the best you can you should get shredded first and worry about building muscle afterwards and if you're new to the gym you're automatically going to start building muscle even on a diet.
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Going by this chart, once you hit 15%, it's time to consider a cut.
The guy at 10 to 12 is in a great place to start a bulk.
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I'm cutting right now, I'm probably going to try to get another 10 lb of fat off before I start my bulk. Could I start bulking right now? Yeah I definitely could, but for how long? Building muscle takes time, a guy who's 10% body fat can bulk for 4-6 months no problem and put on some muscle, the guy who's 15-20% is only going to be able to bolt for like 4 to 6 weeks before they've gotten too fat, and realistically, you're not going to build any noticeable amount of muscle in 4 to 6 weeks. Not even on steroids