Average Down Calculator (Average Cost)
New average price after buying more, and how much to buy to reach a target average
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Calculates your new average cost per share or coin after buying more, and how many more you need to buy to bring the average to a target. Buying below your average (averaging down) and above it (averaging up) use the same calculation.
How to use
- Under "Current holding", enter the "Quantity held" and "Current average price".
- Under "Additional buys", enter the "Buy price" and a quantity or an amount. Press "Add a buy" for more purchases.
- Enter the "Current price" to see the "Unrealised profit or loss", "Return" and "Break-even price".
- Under "Quantity needed for a target average", enter the "Target average price" and the "Price you will buy at" to get the "Quantity to buy" and "Amount needed".
- Set fee rates and fractional quantities under "Options" with "Buy fee rate", "Sell fee rate" and "Quantity step".
How it works
- New average = (quantity held × current average + cost of the new buys) ÷ total quantity. The buy fee is included in the average; the sell fee is taken from the profit or loss.
- Quantity for a target average T = (total cost − T × quantity held) ÷ (T − buy price × (1 + buy fee rate)), rounded up to the chosen step.
- Quantities can have up to 8 decimal places. This is a calculator, not investment advice; taxes and exchange rates are not included.
- Your inputs are saved in this browser on this device.
Questions and answers
- How do I calculate my average cost after averaging down?
- Add the cost of what you hold to the cost of the new buy and divide by the total quantity. Holding 10 shares at 100 and buying 10 more at 80 gives an average of 90.
- How many shares do I need to buy to lower my average?
- Enter the target average and the buy price. In the example above, reaching an average of 90 takes 10 shares bought at 80.
- Why can the target average not be reached?
- The target must lie between your current average and the buy price including fees. No quantity can bring the average below the price you buy at.
- Does it work with fractional shares or crypto?
- Yes. Choose 2, 4 or 8 decimal places under "Quantity step". Buys entered as an amount and the target result are rounded to that step.