Average Cost of Two Buys
Use a quantity-weighted average, not the plain average of the prices. Ten at 70,000 and twenty at 50,000 averages 56,667 — not 60,000.
Your numbers
Average price
56,667
Total quantity
30
Invested
1,700,000
Change
-19.05%
Formula
Average price = (First buy price × First quantity + Second buy price × Second quantity) ÷ (First quantity + Second quantity)
Leaving out commission understates your break-even. Add buying fees into the cost side.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| First buy priceThe unit price on the first purchase. | 70,000 | 0 and up |
| First quantityHow many you bought first; it weights the average price. | 10 | 0 and up |
| Second buy priceThe unit price on the second purchase. | 50,000 | 0 and up |
| Second quantityHow many you bought the second time. | 20 | 0 and up |
Step by step
Quick reference table
Results when only First buy price changes and everything else stays put.
| First buy price | Average price | Total quantity | Invested |
|---|---|---|---|
| 35,000 | 45,000 | 30 | 1,350,000 |
| 52,500 | 50,833 | 30 | 1,525,000 |
| 70,000 | 56,667 | 30 | 1,700,000 |
| 105,000 | 68,333 | 30 | 2,050,000 |
| 140,000 | 80,000 | 30 | 2,400,000 |
What each result means
| Result | At default values |
|---|---|
| Average priceThe quantity-weighted average price — your break-even. | 56,667 |
| Total quantityEverything bought across both purchases. | 30 |
| InvestedEverything you put in; include fees or the return comes out flattering. | 1,700,000 |
| Change (%)How far it moved, measured against the before value. | -19.05 |
Common mistakes
Leaving out commission understates your break-even. Add buying fees into the cost side.
Glossary
- First buy price
- The unit price on the first purchase.
- First quantity
- How many you bought first; it weights the average price.
- Second buy price
- The unit price on the second purchase.
- Second quantity
- How many you bought the second time.
- Average price
- The quantity-weighted average price — your break-even.
- Total quantity
- Everything bought across both purchases.
- Invested
- Everything you put in; include fees or the return comes out flattering.
- Change
- How far it moved, measured against the before value.
Frequently asked questions
Q. How is Average Cost of Two Buys calculated?
Average price = (First buy price × First quantity + Second buy price × Second quantity) ÷ (First quantity + Second quantity) — Use a quantity-weighted average, not the plain average of the prices. Ten at 70,000 and twenty at 50,000 averages 56,667 — not 60,000.
Q. Can you walk through an example?
With First buy price 70,000, First quantity 10, Second buy price 50,000, Second quantity 20, the answer is Average price 56,667.
Q. What do I need to enter?
Enter First buy price, First quantity, Second buy price, Second quantity. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only First buy price moves the answer to First buy price 35,000 → Average price 45,000 and First buy price 140,000 → Average price 80,000. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Leaving out commission understates your break-even. Add buying fees into the cost side.
Related calculators
Tax rates and interest conventions differ by country and product — check your contract for real transactions.