Dollar Cost Averaging Calculator
Simulate fixed periodic investments over your own price series or a modelled return, and compare the average cost and ending value against a single lump sum.
Dollar cost averaging vs one lump sum
| Measure | Averaging in | Lump sum at period 1 |
|---|---|---|
| Amount invested | $18,000.00 | $18,000.00 |
| Units held | 160.6228 | 180.0000 |
| Average cost per unit | $112.0638 | $100.0000 |
| Ending value | $20,267.78 | $22,712.85 |
| Profit or loss | $2,267.78 | $4,712.85 |
| Return on money invested | 12.60% | 26.18% |
Your average cost of $112.0638 compares with a simple average price of $112.5988 across the same periods. Buying a fixed amount each time always gives an average cost at or below the simple average price, because the fixed amount buys more units when the price is low.
Period by period
| # | Price | Units bought | Total units | Invested | Value |
|---|---|---|---|---|---|
| 1 | $100.0000 | 5.0000 | 5.0000 | $500.00 | $500.00 |
| 2 | $100.6667 | 4.9669 | 9.9669 | $1,000.00 | $1,003.33 |
| 3 | $101.3378 | 4.9340 | 14.9009 | $1,500.00 | $1,510.02 |
| 4 | $102.0134 | 4.9013 | 19.8022 | $2,000.00 | $2,020.09 |
| 5 | $102.6935 | 4.8689 | 24.6711 | $2,500.00 | $2,533.56 |
| 6 | $103.3781 | 4.8366 | 29.5077 | $3,000.00 | $3,050.45 |
| 7 | $104.0673 | 4.8046 | 34.3123 | $3,500.00 | $3,570.78 |
| 8 | $104.7610 | 4.7728 | 39.0850 | $4,000.00 | $4,094.59 |
| 9 | $105.4595 | 4.7412 | 43.8262 | $4,500.00 | $4,621.89 |
| 10 | $106.1625 | 4.7098 | 48.5359 | $5,000.00 | $5,152.70 |
| 11 | $106.8703 | 4.6786 | 53.2145 | $5,500.00 | $5,687.05 |
| 12 | $107.5827 | 4.6476 | 57.8621 | $6,000.00 | $6,224.96 |
| 13 | $108.3000 | 4.6168 | 62.4789 | $6,500.00 | $6,766.46 |
| 14 | $109.0220 | 4.5862 | 67.0651 | $7,000.00 | $7,311.57 |
| 15 | $109.7488 | 4.5559 | 71.6210 | $7,500.00 | $7,860.32 |
| 16 | $110.4804 | 4.5257 | 76.1467 | $8,000.00 | $8,412.72 |
| 17 | $111.2170 | 4.4957 | 80.6424 | $8,500.00 | $8,968.80 |
| 18 | $111.9584 | 4.4659 | 85.1084 | $9,000.00 | $9,528.60 |
| 19 | $112.7048 | 4.4364 | 89.5447 | $9,500.00 | $10,092.12 |
| 20 | $113.4562 | 4.4070 | 93.9517 | $10,000.00 | $10,659.40 |
| 21 | $114.2125 | 4.3778 | 98.3295 | $10,500.00 | $11,230.46 |
| 22 | $114.9740 | 4.3488 | 102.6783 | $11,000.00 | $11,805.33 |
| 23 | $115.7404 | 4.3200 | 106.9983 | $11,500.00 | $12,384.03 |
| 24 | $116.5120 | 4.2914 | 111.2897 | $12,000.00 | $12,966.59 |
| 25 | $117.2888 | 4.2630 | 115.5527 | $12,500.00 | $13,553.04 |
| 26 | $118.0707 | 4.2348 | 119.7875 | $13,000.00 | $14,143.39 |
| 27 | $118.8579 | 4.2067 | 123.9942 | $13,500.00 | $14,737.68 |
| 28 | $119.6502 | 4.1788 | 128.1730 | $14,000.00 | $15,335.93 |
| 29 | $120.4479 | 4.1512 | 132.3242 | $14,500.00 | $15,938.17 |
| 30 | $121.2509 | 4.1237 | 136.4479 | $15,000.00 | $16,544.43 |
| 31 | $122.0592 | 4.0964 | 140.5442 | $15,500.00 | $17,154.72 |
| 32 | $122.8730 | 4.0692 | 144.6135 | $16,000.00 | $17,769.09 |
| 33 | $123.6921 | 4.0423 | 148.6558 | $16,500.00 | $18,387.55 |
| 34 | $124.5167 | 4.0155 | 152.6713 | $17,000.00 | $19,010.13 |
| 35 | $125.3468 | 3.9889 | 156.6602 | $17,500.00 | $19,636.87 |
| 36 | $126.1825 | 3.9625 | 160.6228 | $18,000.00 | $20,267.78 |
Units bought each period = contribution ÷ that period's price, and the average cost is total invested ÷ total units. Worked check: three $100 buys at prices of 10, 12.50 and 8 buy 30.5 units, giving an average cost of $9.8361 against a simple average price of $10.1667. Fees, taxes and dividends are excluded. Arithmetic only, not investment advice.
What is the Dollar Cost Averaging Calculator?
The ByteTools Dollar Cost Averaging Calculator models what happens when you invest the same amount at a regular interval instead of all at once.
- Paste a real price series or model a smooth expected return
- Monthly, fortnightly, weekly, quarterly or annual contributions
- Running average cost per unit against the simple average price
- Side-by-side comparison with investing the same total as one lump sum
- Period-by-period table of units bought, totals and value
- Entirely offline: no market data is fetched and nothing is uploaded
How to use the Dollar Cost Averaging Calculator
- 1
Choose your currency and whether to model a constant return or paste your own price series.
- 2
Enter the amount you invest each period and how often you invest.
- 3
For the modelled path, set the number of periods, the starting unit price and the expected annual return.
- 4
For your own data, paste the prices into the price series box — one per line, or separated by commas.
- 5
Compare the averaging column against the lump-sum column, then open the period-by-period table for the detail.
About the Dollar Cost Averaging Calculator
The ByteTools Dollar Cost Averaging Calculator models what happens when you invest the same amount at a regular interval instead of all at once. Each period it buys contribution ÷ price worth of units, tracks the running average cost, and shows the ending value beside what one lump sum at the first price would have produced.
You can drive it two ways: paste a real price series, one price per period, or model a constant expected return and let it generate the path. Either way the period-by-period table shows the units bought, the running total and the value at every step, which is where the averaging effect becomes obvious.
It is aimed at anyone running a monthly investing plan and wanting to see the arithmetic behind it. Everything happens in your browser and nothing is uploaded. These are estimates for planning, not investment advice, and no real prices are fetched.
Frequently asked questions
What is dollar cost averaging?
It means investing a fixed amount of money at a regular interval regardless of price. Because a fixed sum buys more units when prices are low and fewer when they are high, your average cost per unit ends up at or below the simple average of the prices you paid.
How do you calculate the average cost in dollar cost averaging?
Divide the total money invested by the total units bought. Three $100 purchases at prices of 10, 12.50 and 8 buy 30.5 units for $300, giving an average cost of $9.84 against a simple average price of $10.17.
Is dollar cost averaging better than a lump sum?
Historically, lump-sum investing wins more often in rising markets simply because the money is invested for longer. Averaging in reduces the risk of buying everything at a peak and is easier to stick to, which is why this tool shows both outcomes side by side.
Does this calculator use real share prices?
No. It never connects to the internet. Either you paste your own price history or you let it model a constant return, which keeps the tool fast, private and usable offline.
Can I use this for crypto or index funds?
Yes. The maths is the same for any asset you buy in fractional units at a quoted price, so it works equally well for index funds, ETFs and crypto. Fees and spreads are not included, so subtract those separately.
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