Stock Average Calculator
Calculate a new average cost basis after buying additional shares at a new price.
- Last reviewed
- July 8, 2026
- Cost
- Free to use
- Data
- Runs in your browser
New Average Cost
Enter valid inputs
Total Shares
Enter valid inputs
Total Cost Basis
Enter valid inputs
New Purchase Cost
Enter valid inputs
Methodology
How this calculator handles inputs
This calculator uses the values you enter above and applies the formula explained in the guide below. Results update in the browser and are intended for quick planning, comparison, and sanity-checking.
- Use consistent periods, currencies, and units across inputs.
- Review any assumptions before using the result in a decision.
- Recalculate when rates, prices, tax rules, or business terms change.
Important note
This tool provides general planning information only. It is not tax, legal, financial, accounting, or investment advice. Check the current rules for your location and speak with a qualified professional before making a high-stakes decision.
Guide
How it works
Use this calculator to find your new average stock cost after buying more shares.
What this calculator does
The stock average calculator combines your current shares and average cost with a new purchase.
Stock Average Formula
Average Cost = Total Cost Basis / Total Shares
Example calculation
If you own 100 shares at an average cost of 40 and buy 50 shares at 32, the calculator estimates your new average cost.
When to use this calculator
- averaging down
- averaging up
- tracking cost basis
- planning additional purchases
FAQs
Is average cost the same as tax basis?
It can be related, but tax basis rules vary. This calculator is a planning estimate.
Explore more
More calculators in this topic
Continue exploring
Related calculators
Explore the next calculations most relevant to this topic.
investments
Stock Profit Calculator
Calculate stock profit or loss from shares, buy price, sell price, and fees.
investments
Dollar-Cost Averaging Calculator
Estimate shares purchased, average cost, and ending value from investing a fixed amount over time.
investments
Capital Gains Calculator
Calculate capital gain or loss from cost basis, sale value, and selling fees.