Irish Calculators
Saving & investing

Average Share Purchase Price Calculator

Combine purchase quantities, prices and attributable fees to find average economic cost per unit. The calculation excludes sales, tax-lot rules and automatic adjustments for stock splits.

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Your numbers

One row per purchase. Use one asset and one currency; no sale rows or thousands separators.
Display currency only. Convert all inputs to this currency before calculation.
Your figures stay on this device.

How the calculation works

A purchase average should weight each price by the number of units bought. This tool also includes attributable purchase fees, producing an economic acquisition cost per unit for one asset across several purchases.

Average cost = sum(quantity × unit price + purchase fees) ÷ sum(quantity).

  1. Cost each purchase

    Multiply the row quantity by its unit price and add that row's purchase fee. A fixed transaction fee therefore affects a small purchase more per unit.

  2. Combine quantities and costs

    Add all purchased units and all acquisition costs. Larger purchases carry greater weight, which is why a simple average of quoted prices can be misleading.

  3. Calculate cost per unit

    Divide total acquisition cost by total units. The result reconciles the combined purchase history without inventing a current market price.

Worked example: Check Average cost per unit

Sample inputs demonstrate the method. They are not a forecast or product offer.

The first example buys ten units at 10 and twenty units at 20 without fees. Total cost is 500 for thirty units, giving approximately 16.6667 per unit; the larger purchase receives twice the weight.

Quantity, price per unit, purchase fee
10,10,0 20,20,0
Currency for all amounts
Euro (EUR)

Expected result

Average cost per unit
€16.666667
Worked example: Check Average cost per unit

Sample inputs demonstrate the method. They are not a forecast or product offer.

Quantity, price per unit, purchase fee
2,50,10 3,30,0
Currency for all amounts
Euro (EUR)

Expected result

Average cost per unit
€40.00

Understanding your result

The average is an economic cost for the purchases included, not a historical average of market quotes. It changes when purchases or attributable fees are added.

Sales, tax-lot matching and realised gains are outside this model. If shares have split, restate quantities and prices consistently before combining earlier and later purchases.

Questions you might have

What does the result include?

Calculate the quantity-weighted purchase price of one asset, including attributable purchase fees.

Which limits should I check?

Purchases only. Stock splits must already be reflected consistently in quantities and prices.

Choosing the right inputs

Quantity, price per unit, purchase fee
Enter quantity, price per unit and purchase fee on each row. Do not use a heading or thousands separators that would create extra columns.
Currency for all amounts
Use one currency for every purchase and fee. Selecting another display currency changes labels only; it does not convert past transaction amounts.

Common mistakes to avoid

  • Do not enter sale proceeds as negative purchases.
  • Do not use a fee per unit in the purchase-fee column when the actual fee was a total per transaction.

Assumptions to check

  • Purchases only. Stock splits must already be reflected consistently in quantities and prices.
  • All calculations run on your device. Figures are scenarios based on your inputs, not investment recommendations.

Sources and method

Read our calculation and testing approach.