Blend several buys into a single average unit cost, or find how much to buy to bring your average down to a target.
Enter your buys
Add each buy as a quantity and price, or switch to target mode to average down.
Weighted-average cost across lots. The target mode shows the extra units needed to move your average to a chosen level. Fees and taxes are excluded.
Average cost 18.67 £ · Total quantity 150Weighted-average cost basis. Blend multiple purchase lots into one average unit cost, or find how much to buy to reach a target average. Instant in-browser calculation, no account. Last updated: 13 July 2026.
⚖︎ Results are for informational purposes and do not constitute tax advice. For specific situations, consult a licensed accountant or the relevant tax authority.
The average cost is the total spent divided by the total quantity across all your purchase lots:
Buying 100 @ £20 then 50 @ £16: (100×20 + 50×16) ÷ 150 = 2,800 ÷ 150 ≈ £18.67 average cost.
It is the weighted average: add up the amount spent on every lot (quantity × price), then divide by the total quantity bought. Bigger lots pull the average toward their price.
Switch to the target mode: enter your current quantity and average, a target average and the price you can buy at. The tool shows how many extra units to buy to reach that average — if it is reachable at that price.
You can only pull the average toward the new buy price. If the target is below the price you are buying at (when averaging down), no quantity will get you there — you would need a lower purchase price.
Yes. The maths is the same for any position built from multiple purchases — shares, crypto, or stock/inventory cost basis. It ignores fees and taxes unless you fold them into the price.