Taking inspiration from Kath @ The Courage to Start, I'm crunching the numbers.
My BMR (Base Metabolic Rate) is 1572. To work yours out, go here.
I will be eating approximately 1200 calories a day.
To lose 1kg a week - I want to lose 11 more kilos in the 12 weeks, so that works - I need a deficit of 7000 calories each week. Simply by eating only 1200 calories a day, that gives me a deficit of 372x7 = 2604 calories.
7000 - 2604 = 4396 calories to burn in exercise.
5 days a week I do the home-to-school-and-back walk twice, even on a very slow day this would be at least 100 calories each day, so 500 calories a week. On Mondays and Wednesdays I walk or cycle to the swimming pool and back for the kids' swimming lessons, that's 1.8km, at least 200 calories each time, so another 400 calories a week. In Term 2, this might stop but it will be replaced with walking to soccer training instead. Another 150 calories for the bike ride to the shops and back once a week.
1050 calories in incidental exercise. 4396 - 1050 = 3346 calories.
If I allow 1000 calories for a Super Saturday, and allow for a rest day, that leaves me with 2346 calories between the other five days.
2346/5 = 469.2 calories per session! I'm aiming for 500 to give me some leeway all around.
Just shows you how important incidental exercise is, too, I'd have to do much longer sessions if I was driving everywhere. I've always walked this much, the problem is I was eating too much. By keeping that under control, I'm going to do fine.