🔄 SIP / Dollar Cost Averaging Calculator

A Systematic Investment Plan (SIP) is a method of investing a fixed amount at regular intervals — typically monthly — into a fund or asset, regardless of its current price. In the US, the same approach is called Dollar Cost Averaging (DCA). The two terms describe identical mechanics from different market contexts: SIP is the term used in Indian mutual fund markets; DCA is the equivalent term used in the US and internationally.

The core principle is simple: because you invest the same dollar amount each period, you automatically buy more units when prices are low and fewer when prices are high. Over time, this smooths your average purchase price below the asset's average price — a mathematical property of fixed-amount periodic investing known as the harmonic mean effect. More practically, it removes the need to time the market and makes investing a habit rather than a decision you have to make each month.

This calculator projects the future value of any regular monthly investment, with an optional initial lump sum. Enter a monthly amount, an annual return rate, and a time period — the chart and summary update instantly.

The SIP calculation uses the future value of an annuity due — a series of payments made at the beginning of each period. The formula is:

FV = P × ((1 + r)ⁿ − 1) / r × (1 + r)

• FV — the final corpus (total value at the end of the investment period)
• P — the monthly contribution amount
• r — the monthly interest rate (annual rate ÷ 12)
• n — the total number of months (years × 12)

If an initial lump sum is also invested, its future value — L × (1 + r)ⁿ — is added to the SIP result.

Worked example (calculator defaults): $500/month, 10% annual return, 20 years, no lump sum.

• Monthly rate r = 10% ÷ 12 = 0.8333%
• n = 20 × 12 = 240 months
• FV = 500 × ((1.008333)²⁴⁰ − 1) / 0.008333 × 1.008333 ≈ $382,956
• Total invested: $500 × 240 = $120,000
• Total returns from compounding: $262,956
• Wealth ratio: $382,956 / $120,000 = 3.19×

Over two decades, compounding more than doubles the contribution amount — you put in $120,000 and the market returns an additional $263,000 on top of it. The wealth ratio shows how many times your invested capital has multiplied; at 10% over 20 years, each dollar invested becomes roughly three dollars.

The primary advantage of DCA is not mathematical — it is behavioral. Investing a fixed amount each month means you never have to decide whether prices are "right" before buying. This removes the single most common mistake retail investors make: waiting for a better price that may never come, or panic-selling during a downturn and missing the recovery.

A simple example illustrates the price-averaging mechanics. Suppose you invest $500/month into an index fund over three months with these prices:

• Month 1: price $100 → buy 5.00 units
• Month 2: price $80 (market drops) → buy 6.25 units
• Month 3: price $110 → buy 4.55 units

Total invested: $1,500. Total units: 15.80. Average cost per unit: $94.94. The average market price over those three months was ($100 + $80 + $110) / 3 = $96.67. Your average cost of $94.94 is lower — because you bought more units in month 2 when the price was lowest. This is the harmonic mean effect: fixed-amount investing produces a lower average cost than fixed-unit investing when prices fluctuate.

The key condition: this advantage materialises when prices eventually recover above the dip. DCA does not protect against a sustained, permanent decline — it accelerates losses if you keep buying into a falling asset that never recovers. For broad market index funds with long time horizons, price recovery has been historically reliable. For individual stocks or speculative assets, it is not.

Research consistently shows that investing a lump sum immediately outperforms DCA on average — roughly two-thirds of the time over any given period — because markets trend upward over time and cash held waiting to be invested earns less than it would in the market. A Vanguard study found that lump sum investing outperformed a 12-month DCA plan by an average of 2.3 percentage points across US, UK, and Australian markets.

Despite this, DCA is not irrational. It is the only realistic option for most people who do not have a large sum to invest at once — they invest from each paycheck as they earn. And for investors who receive a windfall, DCA reduces the psychological risk of regret: the worst outcome is investing everything at a market peak and watching it fall. DCA trades the expected return advantage for reduced variance in outcomes.

The practical recommendation: if you have a lump sum, invest it. If you are building from monthly savings, invest consistently on a fixed schedule. Either approach, sustained for years, beats holding cash. Use the lump sum field in this calculator to model a hybrid approach — an initial investment combined with ongoing monthly contributions.

What is dollar cost averaging and does it actually work?

Dollar cost averaging means investing a fixed dollar amount at regular intervals regardless of price. It works in the sense that it reduces the average cost per unit compared to random-timing or infrequent lump-sum purchases during volatile periods, and it eliminates the behavioural risk of trying to time the market. Studies show that lump-sum investing outperforms DCA on average when the investor has the full amount available upfront, because markets rise more often than they fall. DCA's main value is making investing automatic and emotionally sustainable — consistency over years matters more than entry-point optimisation.

What is the SIP formula and how is the final corpus calculated?

The SIP formula is FV = P × ((1 + r)ⁿ − 1) / r × (1 + r), where P is the monthly contribution, r is the monthly interest rate (annual rate ÷ 12), and n is the total months. It is the future value of an annuity due — a series of payments made at the start of each period. For example, $500/month at 10% annual return for 20 years produces a corpus of approximately $382,956, of which $120,000 is your total contributions and $262,956 is compounding returns. If you also invest an initial lump sum, its future value — Lump × (1 + r)ⁿ — is added to the SIP result.

Is it better to invest a lump sum or spread it out over time?

If you have a large sum available, investing it all immediately outperforms spreading it over months roughly two-thirds of the time, because markets trend upward and cash waiting to be deployed earns less than invested capital. However, the difference is usually modest over long periods, and many investors find DCA less stressful. If you are building wealth from regular income rather than a windfall, DCA is simply the natural approach — you invest what you have when you have it. The more important decision is to invest consistently at all, rather than the timing of any single investment.

How much should I invest per month to reach a target amount?

Rearrange the SIP formula to solve for P: the monthly amount needed to reach a target FV is P = FV × r / (((1 + r)ⁿ − 1) × (1 + r)). In practice, use this calculator iteratively — enter your target corpus as the final corpus, set your return rate and time horizon, then adjust the monthly contribution slider until the projected corpus matches your goal. For example, to reach $500,000 in 20 years at 10% annual return, you need approximately $653/month. To reach the same amount in 15 years, you need approximately $1,188/month — a useful illustration of why starting earlier requires significantly less each month.

What annual return rate should I use for DCA projections?

The S&P 500 has returned approximately 10% per year nominally and ~7% after inflation over the long run. For a conservative projection, 6–7% is appropriate. For a moderate projection, 8–10% is typical. Because SIP projections are highly sensitive to the assumed return rate — small differences compound significantly over 20–30 years — always run multiple scenarios. At 7%, $500/month over 20 years grows to roughly $261,000. At 10%, the same inputs produce $382,956. The gap illustrates why the assumed return rate is the single most important input in any long-term projection.