BMR + TDEE

A solid counting of calorie intake is your best bet. The answer will be in your food diary and what your body weight scale tells you.

Really calculators are just estimates and you may need to adjust up or down.
This is the one I like:
https://www.iifym.com/iifym-calculator/

Estimating TDEE

There are many TDEE calculators available on the interwebz. A couple of good ones are:

http://www.exrx.net/Calculators/CalRequire.html
http://scoobysworkshop.com/calorie-calculator/ (but ignore the rest of the site as it's full of bs).

Note however, these are all estimates of averages. The best determination of what your TDEE are your results. If you have been tracking for a while, you should be able to look back over a period of time and calculate what YOUR actual TDEE is. For example, say I lost 8lb over a 10 week period while eating an average of 2,000 calories a day. My TDEE would be: 2,000 x 7 days x 10 weeks (140,000) which represents the total calories consumed over the 10 week period plus 8 x 3,500 (28,000) which represents my weight loss expressed as a deficit using the 3,500 calories per pound approximation. My total expenditure over that period would be 168,000 (the 140,000 plus the 28,000) divided by 70 (7 days x 10 weeks) = 2,400 per day. This would approximate my TDEE. Obviously this number should be tweaked up or down if there is any significant change in activity. It also assumes that you have been logging your intake accurately.

As noted above, general recommendations for weekly weight loss goals should be based on a number of factors, the main one of which is how much weight you have to lose. Using the ‘TDEE” method it is a good rule of thumb to take a cut of 20% off your TDEE, which will represent your deficit, to get to your calorie target. However, at a low BF%, this will probably be too high and a 10% cut would be more appropriate. Conversely, at when someone has a significant amount of body fat to lose, a 30% cut may well be appropriate.

To customize your goals in order to be able to use this TDEE based method on MFP, go to My Home -> Goals-> Change Goals-> click Customize and update to the appropriate calorie target.

Note:
It is important to not to have too large of a deficit to minimize the negative impact of weight loss, that may include risk of loss of LBM (which can be mitigated to a large degree with strength training and adequate protein), hormonal disruption, metabolic adaptation, lower gym performance, possible lack of sufficient nutrients, lack of adherence and generally being grumpy. As noted above however, the ‘best’ deficit for an individual will depend on personal circumstances and also their sensitivity to large deficits. From my personal experience, when I got down to about a 22% BF%, I could not handle prolonged deficits of much more than about 15% on average as my gym performance suffers and I tend to whine and pout at that stage. Others may be perfectly OK on a 20% cut at that BF%.

Also, if your results are not in line with what you expect, tweak your targets up or down as appropriate.

EditedToAdd:
BMR (Basal Metabolic Rate): The number of calories you burn at complete rest.
EAT (Exercise Associated Thermogenesis): Caloric requirements of training, or training expenditure.
NEAT (Non Exercise Activity Thermogenesis): Caloric requirements of activity that is not planned exercise. Vacuuming, driving, brushing your teeth, for example.
TEF/DIT (Thermic Effect of Feeding or Diet Induced Thermogenesis): Caloric expense of eating/digestion.
TDEE: (Total Daily Energy Expenditure) = Sum of the above. BMR+EAT+NEAT+TEF

****Not my original thoughts or words. Just some useful information from some really smart people. SideSteel and Sarauk2sf