To get a fairly exact calculation follow these steps:
Step 1: Calculate your Basal Metabolic Rate (BMR). This is the number of calories that's needed to keep your body functioning without you doing any activity at all. It doesn't take muscle mass into consideration so it will underestimate the calories needs for very muscular people and overestimate them for obese people.
The formula is:
Women: BMR = 655 + ( 9.6 x weight in
kilos ) + ( 1.8 x height in cm ) - (
4.7 x age in years )
Men: BMR = 66 + ( 13.7 x weight in
kilos ) + ( 5 x height in cm ) - ( 6.8
x age in years )
Women: BMR = 655 + ( 4.35 x weight in
pounds ) + ( 4.7 x height in inches )
- ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in
pounds ) + ( 12.7 x height in inches )
- ( 6.8 x age in year )
So for example if you're a 32 year old man who is 181 cm tall and weighs 89 kilos, the BMR would be 1973.
Step 2: Calculate your Physical Activity Level (PAL). This is done by looking at the BMR value for the different activities you do each day.
Here's some example of activities and what BMR value they have:
- Sleeping, lie down silently 0.9
- Sit silently, drive, watch tv 1
- Office work sitting down 1.5
- Cooking, eating 2
- Shower, get dressed, light household work, work standing up 2.5
- Walking on flat ground, cycle 16 km/h 4
- Aerobics low impact 5
- Jog 7 km/h 7
- Ice hockey game, basketball game 8
- Football game, jog 10 km/h, swimming breaststroke 10
- Cycle 25-30 km/h 12
- Running 16 km/h 16
So for example if you spend 8 h sleeping, 6 h drive & watch tv, 8 h office work, 1.5 h light household work and 0.5 h walking, the total BMR value for one day is 27.2 (8*0.9 + 6*1 + 8*1.5 + 1.5*2.5 + 0.5*4). Divide this by 24 hours and you get the average PAL value for a day, which in this case is 1.13.
Step 3: Multiply the average PAL value with the BMR value and you'll get the number of calories you can eat per day to maintain your weight:
1.13 * 1973 = 2229.49 kcal.