A quoted-price average is not necessarily your average cost per unit. Investment lots can have different prices and quantities. The purchase-lot worksheet totals money invested and units acquired, then divides those totals.
Record actual amount and unit price
Use amounts from the same instrument and currency. Units equal amount divided by price. If fees reduce the money buying units, adjust the amount consistently. The worksheet does not fetch confirmations or infer commissions, so preserve the original transaction records.
Divide totals, not prices
Equal cash amounts buy more units at a lower price. A 100 purchase at 10 buys 10 units; another 100 at 20 buys five. Total invested is 200 and total units are 15, giving about 13.33 per unit instead of a simple price average of 15.
Keep arithmetic separate from tax accounting
The result is a weighted arithmetic average. Sales, splits, distributions, lot selection and local cost-basis rules are not modeled. Dollar-cost averaging does not guarantee a profit or prevent loss. Use the CSV to review input lots, not as a replacement for official statements or tax records.
Worked example
Scroll the table horizontally on small screens to see every column.
| Amount | Price | Units |
|---|---|---|
| 100 | 10 | 10 |
| 100 | 20 | 5 |
| 200 total | 13.33 average cost | 15 total |
Fees, sales and jurisdiction-specific tax-lot accounting are excluded.
Sources and checks
Examples are illustrative and can be checked with the linked tools. Read each tool’s assumptions before applying its result. How we verify methods.