The conservative approach is 25% of gross pay. Careful attention to what is included and what is not included in the rent makes a difference.
However, using a budget and looking at your expenditures each month so you can better plan where your money goes are mportant tools.
here is a reference to affordable housing's view...
If it helps, a guide-line when some one is buying a house, lenders don't like to see the total cost of the housing expense, and in your case include the utilities to be above 36% of your income.