平均成本計算機
加碼既有部位時,快速計算新的平均成本與投入總額。
Try the calculator
Run the numbers yourself with the inputs below.
Overview
The Average Down Calculator computes the new weighted average cost per share after one or more additional purchases.
How it works
New Average = (Existing Cost + Additional Cost) / Total SharesEach buy order is weighted by the number of shares purchased, so larger orders pull the average toward their price more strongly than small orders.
Worked example
You hold 100 shares with an average price of 50, then buy 50 more shares at 40.
= Total cost is 100 x 50 + 50 x 40 = 7,000. Total shares is 150. New average price is about 46.67.
When to use it
- Plan how an additional buy at a lower price will move your average cost
- Decide how many shares you need to buy to reach a target average price
- Reconcile multiple partial fills from a dollar-cost-averaging plan
Frequently asked questions
Is averaging down always a good idea?
No. A lower average price only helps if the underlying thesis is still valid.
Does the calculator account for fees and taxes?
It does not. Add commissions, spreads, and any tax cost to the buy prices yourself if you need a precise post-fee average.
Can I use it for crypto or fractional shares?
Yes. The formula is unit-agnostic, so you can enter fractional quantities such as 0.25 BTC or 1.5 shares.