Experience will teach you how many hours it takes to do various jobs. In the mean time there are pricing guides available and some techniques you can use.
This book contains a guide that shows a wide range of jobs and how they were priced. You can use these for comparison purposes to price your work. If you visit the resources section you’ll find estimating books for sale designed for the construction industry.
Remember that estimating handyman work is not an exact science. Every task is different and every job will have unforeseen problems. Here is a technique you can use: When you’re stuck, round off the job in your mind. Stop trying to figure out what the exact cost will be and start thinking in round numbers. Ask yourself if this work looks like a half day or a full day job. Will it take one day or two? This will give you a starting point for your estimate. Next, add an hour or two as a cushion.
You can also try telling your customer that you’re not sure how long the work will take. Tell him that it may take as long as a full day (for example) and how much that will cost. Reassure him that you will only charge for the actual time spent. In this scenario you’re working by the hour. If he insists on a firm commitment for the entire job, quote the full day rate and negotiate from there.
You’re in the driver’s seat. If the work is unpredictable and the client appears to be unreasonable, quote high to cover yourself. If he accepts, great! If not, move on to the next.