Handymen should add a markup to materials rather than charging cost, because sourcing, picking up, storing, returning and warrantying materials takes time and carries risk. The right percentage depends on your market and overhead, and you should show it clearly on quotes.
Why materials at cost loses money
Materials involve a trip, loading, time at the counter and the risk of wrong parts. If you only pass through the receipt, all of that work is unpaid.
Choosing a markup
Many contractors use a flat percentage on materials, sometimes scaled down for expensive items. Check what other local contractors do, then pick a percentage that covers pickup time, handling and returns.
Worked example: materials cost $80 and you apply a 20% markup, so you charge $80 x 1.20 = $96. If it takes 30 minutes to buy the parts and your rate is $80 an hour, the markup of $16 does not even cover the trip, so some small jobs need a minimum procurement charge instead.
The return trip problem
Wrong parts happen. Charge for trips, or build them into your markup, instead of eating them.
Trade accounts
Pro accounts at supply houses often have lower prices than retail. Passing on part of the savings and keeping part is common. Track the costs carefully; see expense tracking.
Show it transparently
Either itemize materials plus a handling line, or present marked-up prices. Do what is permitted in your state; some states regulate how materials are billed on certain contracts. See hourly rate guide.
FAQ
How much markup should a handyman charge on materials?
There is no universal number. Choose a percentage that covers sourcing time, handling, returns and risk, and compare it with local contractors.
Should I show the markup on the quote?
Either approach works if it is clear and legal in your state. Many show materials and a separate handling line.
Can I mark up customer-supplied materials?
Usually you cannot mark up what you did not buy, but you can state in the quote that you do not warranty customer-supplied materials.
What if a part is returned?
Decide beforehand who bears return time. Many handymen charge for the trip or include it in their handling fee.