Average Purchase Price Calculator
Work out the weighted average price across several purchases of the same holding, before and after dealing fees, and see where you stand today.
Formula and method
Average excluding fees = Σ(quantity × price) ÷ Σ(quantity).
Average including fees = (Σ(quantity × price) + Σ fees) ÷ Σ(quantity). This is your break-even price per unit.
Unrealised gain or loss compares the current value of the total quantity with everything you paid, fees included.
Worked example
Buy 10 units at €100, then 20 units at €130.
Total paid = €1,000 + €2,600 = €3,600 for 30 units, so the average is €3,600 ÷ 30 = €120.
Note this is below the €115 simple mean of €100 and €130 only when the cheaper purchase is larger — here the larger purchase was the more expensive one, so the weighted average sits above it.
FAQ
Frequently asked questions
How is an average purchase price calculated?
Divide the total amount paid by the total number of units bought. It is a weighted average, so larger purchases influence it more than small ones.
Should dealing fees be included?
Both figures are shown. The average excluding fees reflects the market prices you paid; the average including fees is your true break-even price per unit.
What is dollar-cost averaging?
Buying a fixed amount at regular intervals. It buys more units when prices are low and fewer when they are high, which usually leaves the average below the simple mean of the prices paid.
Does this handle sales?
No. It covers purchases only, so it shows the cost basis of what you have bought rather than realised gains on disposals.
Is this a tax cost basis?
Not necessarily. Tax rules vary: some jurisdictions require average cost, others FIFO or share-pooling rules. Check with a tax adviser.
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