What's actually going on
This is a normal place to get stuck, and it's fixable in your existing sheet — no new software or barcode system required. If you're tracking who has your sample boards, stain chips, or cabinet doors, a spreadsheet can hold that information fine: a name, a date, a contact number. What it usually can't do on its own is tell you when something's overdue. There's no column for "when should this come back," so there's nothing to check against today's date.
That's two separate jobs. One is recording who has what — a spreadsheet does that well. The other is being reminded when something is late, which needs a rule comparing two dates. Most sheets are missing the second half, so people assume the whole sheet has failed, when really it's one column short.
Barcodes and QR codes solve a different problem — faster data entry when items move a lot. They don't create the reminder on their own either; something still has to check the due date and flag it.
The smallest fix you can do today
Add three columns to what you already have: date out, due back, and returned.
Set due back as a formula: date out plus however many days you're comfortable lending for. Leave returned blank until the item comes back, then mark it.
Then add a rule that flags anything overdue. In Excel, this is a conditional formatting rule using a formula — Microsoft's own instructions: click "Use a formula to determine which cells to format," then enter a formula that must return TRUE or FALSE, such as one comparing the due-back date to today's date and checking the returned column is empty (Microsoft Support: Use conditional formatting to highlight information in Excel). Anything overdue turns a colour. Open the sheet, scan for the colour, done — no manual date-checking.
When it's worth keeping, cleaning, connecting, or converting
Keep the spreadsheet if you're checking it once a week and a colour-coded overdue list is genuinely enough. For three designers and occasional homeowner loans, this is probably still true.
Clean it if the due-back column and the flag above aren't there yet — this is a data and formula fix, not a new tool, and it's usually a half-hour job.
Connect it if you want the flag to reach you without opening the sheet — for example, a scheduled export or a calendar reminder pulling from the overdue list, so you don't have to remember to check.
Convert to dedicated loan or asset-tracking software only once the sheet itself is genuinely the limit — for instance, if items move so often that manual entry (barcode or not) can't keep up, or several people need to check items in and out at once without overwriting each other's changes. Buying software before adding the due-back date just buys you the same gap with a monthly fee attached.
What "done" looks like
Done means you can open the sheet on a Monday and see, in one glance, everything that's overdue — without mentally checking today's date against every row. You'd know it's working if the number of "someone had this ages ago and forgot" conversations drops, because the sheet is catching that instead of your memory.
If items are usually out for weeks, a weekly look is enough. If they're usually out for a day or two, you'll want the flag to reach you sooner than your next weekly check — that's the point where connecting the reminder, not just adding it to the sheet, starts to matter.