For the record, TDEE stands for 'Total Daily Energy Expenditure.' I have sleeping problems, which essentially require me to get ~12 hours of sleep a day. I'd assume this substantially lowers my TDEE, but I'd like to be able to calculate the effect more precisely. Thank you.
There are several such calculators where you can input the hours you spend sleeping / sitting / standing etc. One example is here.
Please note that even this will not give you a 100 percent accurate number.