Here I am showing you how I do it and I know the question is only about which activity multiplier to use but it seemed easier to do it this way.
Note about Body fat: You will need to get this one as close to the actual value you have as this will all be based off that.
I am using the Katch-McArdle formula. Different websites refer to the value you get as either RMR (Resting Metabolic Rate) or BMR (Basal Metabolic Rate) but it is the same thing.
My weight: 72.2Kg
Body fat: 10%
Formula Lean Body Mass: (Weight x (100-(Body Fat)))/100
((72.2 x (100-10))/100 = 64.98
Formula: BMR = 370 + (21.6 x Lean Body Mass(kg))
370 + (21.6 x 64.98) = 1773.57
This mean that if I were to never get out of bed, not even to go to the bathroom simply being alive will cost me 1773.57 calories per day. In order for this to be correct I will now add a value for activity multiplier which is simply a way to add calories for you moving around, working, and going to the gym. I am adding 1.55 which means I am moderately active. This value is called total daily energy expenditure (TDEE) and for me this is 1773.57 x 1.55 = 2749.0304.
You will notice that a lot of sites will tell you to start with about +500 calories over maintenance mode (This is 99% of the time to much) but I started at maintenance mode itself and added 50 calories/week until I found my perfect value.
Activity Multiplier
A paper on metabolism used a definition of "vigorous exercise" as expenditure of 14.1 to 16.3 kcal/kg of ideal body weight per day.1 Using the rounded figure of 15 Calories per kilogram of body weight, then "vigorous exercise" for a person weighing 150 pounds (68 kilograms) corresponds to 1020 Calories per day. If walking at 4 miles per hour burns about 300 Calories per hour, then you would need to walk 3 hours and 24 minutes to burn off 1020 Calories.
The activity factors for the Calorie Restriction Calculator are:
1.200 = sedentary (little or no exercise)
1.375 = lightly active (light exercise/sports 1-3 days/week, approx. 590 Cal/day)
1.550 = moderately active (moderate exercise/sports 3-5 days/week, approx. 870 Cal/day)
1.725 = very active (hard exercise/sports 6-7 days a week, approx. 1150 Cal/day)
1.900 = extra active (very hard exercise/sports and physical job, approx. 1580 Cal/day)
The activity factor lightly active corresponds to walking 2 hours per day, moderately active corresponds to walking 3 hours per day, very active corresponds to walking 4 hours per day, and extra active corresponds to walking 5 hours per day (20 miles). More strenuous exercises, such as climbing stairs or running, burn more calories per hour. Most people who exercise from 30 minutes to 45 minutes per day are in the "lightly active" category. You can use the CR calculator to determine the number of calories for each level of exercise for your particular weight by subtracting the calories for a specific activity level from the calories for the sedentary option.
REFRERENCES:
Nutritional regulation of the insulin-like growth factors.
What is moderate exercise?