This has been discussed several times on this forum over the years. Use the 'search' box at the top right of the page and look for things like 'how much to charge', 'quotations' 'estimates', etc.
IIRC, the consensus is to have an...
i use a spreadsheet in xl to list out materials + % then estimate number of days/hours to do the job, add a bit on and that's my price.
Gets easier with experience and also if you log materials and time actually used to compare back to...
The thing is if you get your estimate wrong or if customer doesn't take on board that it's an estimate-
( often they steer clear of estimates and want quotes-fixed price ) It's a tough one I think- i am always fretting over the cost -...
Talking with one of the guys in the office about a mysterious boiler fault (runs, ignites, locks out) reminded me of an issue in a new boiler room some years ago. Three new gas boilers all installed at the same time, due to handover to...