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Tool / portfolio maths
DCA and average price calculator
A dollar-cost averaging or DCA calculation can show how multiple purchases change your average entry price. It does not prove that adding more capital is wise. The tool is a maths exercise to make total exposure and blended cost visible before you make a decision.
Runs in your browserNo account · No API key
local only
How to use it
Numbers are clearer when the assumptions are visible.
Start with the default example. Change one input at a time and notice which part of the result moves. Then read the explanation below before using any real-world number.
- Use your account currency consistently.
- Include costs and uncertainty outside the simple model.
- Verify the product’s own contract or fee rules.
Quick answer
The short answer
Average purchase price equals total purchase value divided by total units. Weight each price by its units; separate costs and future returns from this arithmetic.
Input reference and starting values
| Input | Meaning |
|---|---|
| Purchase units | Amount acquired in each purchase |
| Purchase price | Price per unit in one consistent currency |
How a blended average is calculated
The old position’s cost is existing units multiplied by existing average price. The new purchase cost is new units multiplied by new price. Add the costs and divide by total units. The result is a weighted average, so a larger purchase has a larger influence.
The calculation ignores selling, fees, taxes and changes in the asset itself. Treat it as a recordkeeping aid, not a reason to add to a losing position.
Working modelAverage price = (old cost + new cost) ÷ (old units + new units)
DCA changes exposure as well as average price
A lower average price can look emotionally reassuring, but the account now has more money exposed to the asset. If the asset continues lower, the absolute loss can be larger even while the average price improves.
Before adding, write the reason, maximum allocation, time horizon and what would invalidate the thesis. A scheduled contribution plan is different from repeatedly adding because the market moved against you.
In practice
Weighted average, not average of labels
Buying one unit at $100 and two units at $50 costs $200 for three units, so the weighted average is about $66.67 per unit. The simple arithmetic average of the two prices, $75, would be wrong because quantities differ.
Record fees and actual received units separately when they alter your total cost or quantity. A lower average purchase price does not make the asset safer or guarantee a future gain.
Primary references
Continue with original sources.
These links provide definitions and current context. Product rules, regulation and network details can change, so verify time-sensitive information at the source.
Common questions
Before you move on
Is DCA guaranteed to beat a lump sum?+
No. Results depend on the path of prices, contribution timing, fees and the asset’s eventual performance.
Does the calculator include fees?+
No. Add fees separately to your records or use the real transaction statements.
Can I use it for stocks?+
Yes, as a simple weighted-average exercise, provided you account for fractional shares, fees and the broker’s reporting method.
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