That's pretty perceptive...your BMR probably is different now.
If you're using one of the calculators based on the Harris-Benedict formula, it takes into account your age, and makes some adjustments based on that. While there may be some formulas based on body fat percentage, I'm not aware of them, and doubt they would be much more accurate than Harris-Benedict (because body fat is also an estimate).
Bottom line: use one of the age-adjusted formulas, set an appropriate calorie goal (500 calories less than your estimated "active" metabolic rate), and monitor your weight over time. If you're losing at a reasonable rate (around 1 lb per week +/- 0.5 lb), you'll know you're dialed in. If you're losing weight faster, eat just a bit more. If you're not losing weight, back off a bit on the food consumption.
This assumes, of course, that you've got a reasonable exercise program in place too.