Please tell me the procedure to calculate the cost for washing one bedsheet.

I assume that you are doing an exercise in which you are a
hotel manager and must calculate this figure.  If so, you simply need to determine the
costs of washing a full load of sheets.  Then you must find the number of sheets per
load.  This allows you to divide the cost of the full load by the number of sheets,
giving you the cost per sheet.

The costs that you need to
determine
are:

• Water


• Laundry
  Detergent


• Electricity


• Labor. 
  For labor, you need to determine the cost of getting the sheets off the beds, putting
  them in the washer, transferring them to the dryer, and putting them back on the
  beds.

Find these costs, total them, and divide
by the number of sheets.

Depending on how exact you want to
be, you might want to determine the amount of depreciation suffered by the sheet from
washing.  In other words, how much does each wash reduce the life of the sheet?  You
would need to determine how much of the cost of the sheet is depreciated by each wash. 
You would then add that number to the subtotal you already had.