How to use this average buy price calculator
Average unit purchase prices across batches of the same item. Enter the unit price and quantity for each purchase to see the total quantity, total spend, and blended unit cost. All quantities must use compatible units and prices must use one currency.
- Enter the unit buy price values in the labeled fields, using consistent units.
- Load the example to inspect the expected format, then replace it with your own values.
- Select Calculate and check the result alongside its working. Reset starts a fresh calculation.
Average Buy Price formula
Average buy price = Σ(unit price × quantity) ÷ total quantity
A simple average of the two batch prices would be 4.50, but more units were bought at 4. The quantity-weighted price of 4.25 reconciles exactly with total spend when multiplied by 40 units.
Follow the numbers
10 units at 5 and 30 units at 4 cost 170. Their average unit cost is 170 ÷ 40 = 4.25.
Load the example above to inspect the entries, then change one value and calculate again. The result follows your selected method. Display rounding changes how the answer is shown; it does not change the underlying observations or weights.
What to check before using the result
Use equivalent units: individual pieces and boxes cannot share a quantity column unless you convert them first. Returns and fees are excluded.
Keep enough precision in the source values for your task. A result calculated from rounded summaries can only be as precise as those summaries. If a number was mistyped or an observation is missing, correct the inputs and calculate again before copying or exporting the answer.
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Common mistakes to avoid
- Confusing a blank with zero. A real zero is an observation. Missing information is not automatically zero.
- Mixing incompatible scales. Use consistent units, or normalize values before combining them.
- Rounding too early. Keep the original values and round at the result stage.
- Using the wrong weighting. Use equivalent units: individual pieces and boxes cannot share a quantity column unless you convert them first. Returns and fees are excluded.
Frequently asked questions
What formula does this calculator use?
Average buy price = Σ(unit price × quantity) ÷ total quantity. 10 units at 5 and 30 units at 4 cost 170. Their average unit cost is 170 ÷ 40 = 4.25.
What should I check about the method?
Use equivalent units: individual pieces and boxes cannot share a quantity column unless you convert them first. Returns and fees are excluded.
How many entries can I use?
Paste up to 10,000 values, or use up to 100 individual rows when the chosen input method supports them. Numbers must be finite and no greater than 1 trillion in magnitude. Group and old-count inputs have additional whole-number requirements.
Are the displayed decimals exact?
The calculation uses standard floating-point numbers and compensated addition. Results are rounded only for display. Very small values use scientific notation so they do not silently appear as zero. Select the display precision you need, while respecting the accuracy of your original data.
Are my entries saved or sent anywhere?
The calculator performs its arithmetic in your browser. It does not automatically store entries or send them to a server. Copy, print, and CSV actions happen only when you choose them.
Read our calculation methodology for supported precision, validation, and assumptions.