BMR and deficit calorie calculation

I learned something so great!
This helps work out how much you want to eat and/or exercise.
I came about this because Michelle Bridges has said we need to have 7000 calories in deficit per week to lose a kilo. It just seemed insane to me. So I looked into it and this is how it works;

Calculate your BMR (body metabolic rate).. I use this one http://www.bmi-calculator.net/bmr-calculator/metric-bmr-calculator.php

Calories eaten 1200 - BMR 1623 - calories burned 550 = deficit of 973 / 1 kg per week loss
Calories eaten 700 - BMR 1623 - calories burned 550 = deficit of 1473 / 1.5 kg per week
Calories eaten 1200 - BMR 1623 - calories burned 300 = deficit if 723 / 0.5 kg per week

So I can see that if I eat 1200 cals a day, and burn a usual 300 cals, I'll lose half a kilo.
But if I push myself to burn over 500 cals, and not go over my 1200 cals in food, then I will lose a kilo a week!
Now we're talking! I get that, and it motivates me.I 'm sure this knowledge will push me to 500 cals.
And if I eat even less than 1200 cals....and/ or burn more than 500 cals, I'll lose more than a kilo a week.

I feel empowered now.