I will not get into how to calculate calories in food. By now you should have an approximation of how many calories are in the food you eat. Luckily for you there are LOTS of information in Google. Research online and just get a rough number. I may be off by a couple hundred calories in my estimations, but I do not mind, it is working out for me.
Our bodies burn calories on a daily basis so we can perform basic physiological activities such as breathing, using the potty and be alive. The amount of calories your body burns without you doing any work (i.e even if you lay on your bed all day long) is called your BMR (Basal Metabolic Rate). You can look for online BMR calculators to know your BMR, and find out how many calories you must consume to maintain your weight, assuming you sit like a potato all day without doing anything :D.
Now for the interesting part, I want you to go online and look for a TDEE calculator (I recommend trying several so you get a proper average), which uses your age, height, weight, body fat % approximation and activity level (whether you workout on a daily basis, and whether your job is sedentary or has you doing physical activity such as transporting heavy furniture) to give you an approximate of how many calories you ACTUALLY burn on a daily basis with the physical activity you do. This means that besides your BMR (i.e 1800 calories), since you do some sort of physical activity, whether in your job, or in the gym, or both, your body will burn the calories of BMR plus the ones of those activities. The TDEE calculator will tell you how many calories are your maintenance calories, and that is the number you should use to calculate the calories to consume for fat loss (or muscle gain). I RECOMMEND getting a heart rate monitor watch which tells you how many calories you burn, the ones that come with a belt to strap around your chest, not the cheap kind. I used a POLAR F7 watch for a about a year, which helped me get an approximation of how many calories I burn with different workouts, so now I just have to remember and either give or take a couple hundred calories based on the intensity I gave the workout.
After doing all this, you should know how many calories you are consuming and how many calories you are burning. Lets assume you workout every single day and your TDEE tells you that you burn 2400 calories on average per day. If by the end of the day you consume 2400 calories, in the long run you should not gain or lose weight (keep in mind you may be off in your calculations, the calculators are not perfect, so if you end up gaining a little weight re-assess and either eat less, or exercise more). If you end up burning more calories than you consume, you end up in a caloric deficit, on the contrary you would end with a caloric surplus.
Science dictates that if you have a caloric deficit of 500 every day, and 3500 per week, you should loose 1 lb per week. I do not believe this. I believe our bodies are different and some may lose weight faster than others, depending on our metabolism, and how bad we are calculating the calories we take in, and the calories we burn with our workouts! Remember every day adds up so you will end up with either a weekly deficit or surplus. If you have a weekly deficit of 1000 calories on week 1, and the next week a 1000 caloric surplus, it cancels out and nothing happens.
I am just aiming for a relatively small (between 1000-2000) weekly deficit. In the past I would aim for the so claimed 3500 weekly deficit, which led me to lose about 1-2 kg PER WEEK. This was too much, which means I was either underestimating my calories consumed, or working out too much, or both. Also I encourage doing weight lifting at least 3 times per week. If we build muscle, we are more likely to lose fat faster than without any muscle. Also lets face it, slim and muscular looks better than just plain skinny, at least in my humble opinion. There are also other benefits to weight lifting, such as higher strength.
Finally, I do not believe in good and bad foods. Some foods, such as sugary snacks and junk food, is digested faster by our bodies (High Glycemic Index) while others, such as vegetables and protein rich sources, will be digested slower by our bodies keeping us satiated the longest (Low Glycemic Index). I support and live by the concept of IIFYM, meaning I can eat whatever I want as long as I am including some protein rich source in my daily nutrition, and I am eating actual food whenever I can. Occasionally I will just eat chocolate cookies and Chips for dinner. I recommend reading the posts on my 5 minute approach to working out, and the one on how to keep momentum going, to get an idea of how I have been able to get out of the binging cycle I was before starting this life project, and I am back in the fitness track. I am not an expert on the topics I talked above, I still recommend heading over to Google and researching the topics for yourself. See you later!