You do not need accounting software. You need five numbers, updated weekly, that between them tell you whether the business is working and which part to fix.
Each of these answers a different question, and each has a specific corrective action when it moves the wrong way. Tracking more than five is how measurement becomes a hobby that displaces the work.
Resale data is skewed. One item that sold in four hours and one that sat for eleven months produce an average that describes neither, and averaging days-to-sell across a portfolio with a long tail will consistently flatter you.
The median is the honest summary. Track it alongside the worst decile if you want a second number — that decile is where your dead stock lives, and its behaviour is a better predictor of trouble than anything the top half is doing.
Planned margin is what you believed at the point of purchase. Realised margin is what actually landed after price cuts, absorbed shipping, and the items you eventually gave away. The gap between them is the most useful diagnostic you have, because it quantifies exactly how optimistic your buying is.
If planned margin is 35% and realised is 19%, the fix is not to sell harder. It is to lower the maximum you are willing to pay, until the two numbers converge.
A spreadsheet is plenty. Five columns and one row per week beats any tool you will not actually maintain. The failure mode is never insufficient sophistication — it is abandoning the routine after three weeks.
It depends heavily on price tier, so a universal target would be misleading. What matters is the trend in your own number: rising median days-to-sell at a stable price point means your sourcing is drifting toward stock the market wants less.
Resale IQ turns a Vinted listing into one answer: BUY, WATCH, or SKIP — with buy-below price and best sizes.
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