Dollar Cost Averaging Calculator
The price you really paid when you invested the same amount at different prices, against the plain average of those prices.
Results
What this tool does
Put the same sum in every month and you automatically buy more when things are cheap and less when they are dear. The consequence is arithmetic rather than skill: your average purchase price comes out below the average of the prices you bought at. Type the price at each purchase, one per line, say how much you put in each time, and this page shows both averages, the gap between them, and what the whole thing is worth at today's price.
Formula
average price paid = total invested ÷ units bought (this is the harmonic mean of the prices)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
amount | Amount you put in each time | — |
prices | The price at each purchase, one per line | — |
current | Price today | — |
OUT | Average price you actually paid | — |
SA | Plain average of those prices | — |
AD | What the method saved you per unit | — |
AP | The same as a percentage | % |
IN | Put in altogether | — |
UN | Units you ended up with | — |
NP | Purchases | — |
VN | Worth today | — |
GN | Gain or loss | — |
GP | Percentage change | % |
TB | Each purchase | — |
Worked example
- Amount you put in each time100
- The price at each purchase, one per lineJanuary = 10 February = 8 March = 12.5 April = 9 May = 11 June = 7.5
- Price today11
- Average price you actually paid9.3698
- Plain average of those prices9.6667
- What the method saved you per unit0.2968
- The same as a percentage3.07 %
- Put in altogether600.00
- Units you ended up with64.0354
- Purchases6
- Worth today704.39
- Gain or loss104.39
- Percentage change17.40 %
- Each purchase1. January 10 10.0000 2. February 8 12.5000 3. March 12.5 8.0000 4. April 9 11.1111 5. May 11 9.0909 6. June 7.5 13.3333
Limitations
- The calculation runs entirely in your browser. The values you type are never sent to a server.
- This is an informational calculator, not personalised financial advice. Rates, fees, taxes and contract conditions vary between institutions and countries.
Frequently asked questions
Why is the price I paid lower than the average of the prices?
Because a fixed sum of money buys more units when the price is low and fewer when it is high, so the cheap months carry more weight in your average than the dear ones. The figure you end up with is the harmonic mean of the prices, which is always lower than the plain average unless every price was identical. This is the entire mathematical content of the method — no forecasting, no timing, just the arithmetic of buying in fixed amounts.
Does this mean the method beats investing all at once?
No, and the advantage shown here should not be read that way. It compares your average price against the average of those same prices — it says nothing about what would have happened had you put the whole sum in on the first day, which depends entirely on which way the price then went. What this page measures is a real arithmetic effect within the method, not a claim that the method wins.