Any equation is just an estimate
I'm begining to design a meal plan for bulking and gaining muscle mass, but im not sure how many calories i need per day. I know theres an equation for this but i can't find it. Anyways I weight 155 lbs. and I am about 5 ft 9 in.


You're gonna have to determine that for yourself. Record your diet - food content and calorie counts. Weight yourself daily and take an average at the end of the week. Monitor bodyfat. Over time you'll figure it out.
Online Calcs aren't even close for me. I find myself pushing the broad variables up, up, and up just to arrive at what I think is a reasonable figure. Kind of a game. LOL
My guess, to date, is that 5'11", 200 - I need 4,500 daily to maintain. But all this is subject to so much.
"Wait 'till you see special photos of my old man butt in April!"
I have to go above the normal also.. my maintenance amount is around 2000 - of good clean food
Here's one formula..
Harris-Benedict formula (BMR based on total body weight)
Men:
66 + (13.7 * (weight in pounds/2.2)) + (5* (height in inches * 2.54)) - (6.8 * age in years) = BMR
BMR * AL = Maintenace
Women:
655 + (9.6 * (weight/2.2)) + (1.8 * (height * 2.54)) - (4.7 * age) = BMR
BMR * AL = Maintenace
Basal Metabolic Rate (BMR)
BMR is the sum total of all the energy used for these basic bodily functions(1), not including physical activity.
(1)Breathing, digestion, circulation, temperature regulation, cell construction, and every other metabolic process in your body burns calories.
Activity Level (AL):
Sedentary (1.2) - little or no exercise, desk job
Lightly Active (1.375)- light exercise/sports 1-3 days/wk
Mod. Active (1.55) - moderate exercise/sports 3-5 days/wk
Very Active (1.725)- hard exercise/sports 6-7 days/wk
Extr. Active (1.9) - hard daily exercise/sports & physical job or 2 X day training, marathon, football camp, contest, etc.
Here is the link to the equation and calculator..
http://www.bmi-calculator.net/bmr-ca...mr-formula.php
Here is a link to a few more.
http://www.cordianet.com/calculator.htm

Watch out for those damn equations... If you're like me and you have a super fast metabolism, they're usually short by about 500-1000 calories! What I've found to work is develope a diet, stick with it for month or two, see what kind of gains you're making (or lack thereof) and modify it accordingly until you get it right.
"Wait 'till you see special photos of my old man butt in April!"
These "Equations' are meant to be used as "rough guidelines" for the "average" person. No two people are the same so you are gonna have to tweak the number you get, using the formulas, to you. The Katch-McArdle Formula takes into account lean body mass so it's the more accurate one since muscle burns calories by just being there where as fat does not.