Dollar cost averaging calculator
Model the projected outcome of regular monthly contributions and compare it with a one-off lump sum.
Calculator investmentsLogic updated April 2026
This calculator projects the future value of a Dollar Cost Averaging strategy — investing a fixed amount every month over a multi-year horizon. It uses a deterministic future-value-of-an-annuity formulation, so the projected end balance assumes a smooth annual return; volatility is shown for context but doesn't change the projection. An optional lump-sum comparison shows what investing the same total amount upfront would have produced under the same return.
How this is calculated
Formula
End balance = monthlyContribution × ((1 + r/12)^n − 1) × (1 + r/12) / (r/12) where r is annual return and n is total monthsStep-by-step
- Convert the annual return to a monthly rate by dividing by 12
- Calculate the total number of months in the investment horizon (years × 12)
- Apply the future-value-of-an-annuity-due formula above to project the final balance from regular monthly contributions
- Calculate total contributed = monthly × n (the principal you put in over the horizon)
- Subtract total contributed from the projected end balance to derive total returns earned
- If a lump-sum amount is supplied, project its future value separately as initial × (1 + r)^years for the apples-to-apples comparison
- Rounding mode
- ROUND_HALF_UP
- Precision
- 20-digit internal precision (Decimal.js), rounded to 2 decimal places for display
- Logic last reviewed
Assumptions & limitations
What this calculator assumes
- Contributions occur at the end of each month
- Expected annual return is applied deterministically — no random price paths are simulated
- Volatility is displayed for context only; it does not affect the projected final value
- The lump-sum alternative, if provided, is invested in full at month zero
- Taxes, transaction costs, and currency effects are not modelled
What this calculator doesn’t account for
- Deterministic — does not reflect real-world return sequences or sequence-of-returns risk
- Does not show the range of possible outcomes (use a Monte Carlo tool for that)
- Does not account for fees or platform costs
- Does not model taxation of dividends or capital gains during the contribution period
- Does not factor in inflation — projected balances are nominal, not real
Worked example
An investor commits $500/month for 20 years at an assumed 7% annual return, and compares against a lump-sum investment of the same $120,000 total upfront.
| Input | Value |
|---|---|
| Monthly contribution | $500 |
| Investment horizon | 20 years (240 months) |
| Annual return | 7% |
| Lump-sum comparison | $120,000 upfront |
DCA end balance: ~$262,000 — Total contributed: $120,000 — Returns earned: ~$142,000 — Lump-sum end balance: ~$464,000
Under DCA, the early contributions compound for nearly 20 years while the later ones compound for only a few months — the average duration is around 10 years. Total returns are about $142,000 on $120,000 contributed (118% return on principal). The lump-sum scenario invests the same $120,000 at month zero, so all of it compounds for the full 20 years — the result is about $464,000, $202,000 more than DCA. DCA's advantage is psychological and practical (you don't have $120k upfront), not mathematical.
Frequently asked questions
What is dollar cost averaging?
Investing a fixed dollar amount on a regular schedule (typically monthly) regardless of market price. When prices are low you buy more units; when prices are high you buy fewer. The technique is popular for two reasons: (1) it forces consistent saving, and (2) it removes the temptation to time the market. It does not produce higher long-term returns than lump-sum investing in a generally rising market.
DCA vs lump sum — which is better?
Mathematically, lump-sum investing wins about two-thirds of the time over multi-decade horizons because markets rise more often than they fall, and the lump sum gets to compound for the full horizon. But most people don't have a lump sum to deploy — they have monthly income — so DCA is the practical default. If you ever inherit or receive a windfall, the math suggests investing it promptly rather than spreading it across many months.
How often should I invest?
The most common cadence is monthly because it matches typical income cycles and minimises decision fatigue. Investing weekly or fortnightly produces marginally smoother averaging but adds complexity and may incur more brokerage. Investing quarterly or annually is fine if your income is variable. The frequency matters far less than the total amount invested and the time horizon.
Does DCA reduce risk?
It reduces a specific risk — the risk of investing a lump sum just before a market crash and then watching it fall. But it doesn't reduce overall portfolio volatility once the funds are deployed; once you've fully DCA'd in, you're holding the same asset mix as a lump-sum investor. DCA is essentially a behavioural commitment device, not a risk-reduction strategy in the formal portfolio-theory sense.
What return assumption should I use?
For broad equity portfolios over multi-decade horizons, historical real returns have averaged 5–7%, which translates to 7–10% nominal at current inflation. Using 6–8% is reasonable for a diversified equity portfolio; 4–5% for a balanced (60/40) portfolio; 2–3% for very conservative bond-heavy portfolios. This calculator's projection is sensitive to this assumption — try a range to see how outcomes vary.
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