Reinvestment Plan Deposits Calculator

Calculate Reinvestment Plan Deposits for Desired Future Value

Reinvestment Plan Deposits Formula

Formula

\[ A = P \times \frac{(1 + r)^n - 1}{r} \times (1 + r) \\\ \text{Interest} = A - (P \times n) \]

Where:

$A$ — maturity value of the plan
$P$ — monthly deposit amount
$r$ — monthly interest rate (annual rate $\div 100 \div 12$)
$n$ — total number of months (years $\times 12$)

The first formula is the future value of an annuity due: each deposit earns interest from the day it is made, because deposits are assumed to be reinvested at the start of every month. The second line subtracts your total contributions from the maturity value to isolate the interest earned.

Reinvestment Plan Deposits – Calculation Example

Example: you deposit $500 at the beginning of every month into a reinvestment plan paying 6% per year, compounded monthly, for 5 years.

\[ r = \frac{6}{100 \times 12} = 0.005 \quad n = 5 \times 12 = 60 \]

\[ A = 500 \times \frac{(1.005)^{60} - 1}{0.005} \times 1.005 \approx 500 \times 70.1189 \approx 35{,}059.44 \]

\[ \text{Interest} = 35{,}059.44 - (500 \times 60) = 5{,}059.44 \]

Result: after 5 years the plan matures at approximately $35,059.44, of which $30,000.00 is your own money and $5,059.44 is interest earned.

How to Use the Calculator

Enter your Monthly Deposit Amount — the fixed sum you plan to invest each month.
Enter the Annual Interest Rate your plan offers, in percent (e.g. 6 for 6%).
Enter the Investment Term (Years) — how long you will keep making deposits.
Read the Maturity Value (the total the plan will be worth) and the Total Interest Earned (growth above your own deposits).

What Is a Reinvestment Plan?

A reinvestment plan is a savings scheme in which you make regular deposits — typically monthly — and the interest earned is automatically reinvested rather than paid out. Instead of receiving interest in cash, the interest is added to your balance and itself earns interest in the following periods. This creates a compounding effect: each month your deposited money, plus all previously earned interest, works together to generate returns.

This structure is common in recurring deposit schemes offered by banks and in dividend reinvestment plans (DRIPs) for stocks and mutual funds. It appeals to savers who want a disciplined, hands-off approach: you commit to a fixed deposit each period, and reinvestment does the rest. The result is that even modest monthly contributions can grow into a substantial sum over several years.

Because deposits are made at the beginning of each period (an annuity due), each deposit compounds for one extra month compared to an end-of-month deposit. That is why the formula multiplies by $(1 + r)$. The interpretation of the result is straightforward: the Maturity Value is what your account will hold at the end of the term, and the Total Interest Earned shows how much of that value came from compounding alone.

Assumptions and Limitations

Fixed deposits: the calculator assumes you deposit exactly the same amount every month, with no skipped or extra payments.
Fixed rate: the interest rate must remain constant for the entire term. Variable-rate or stepped-rate plans will produce different results.
Monthly compounding: the annual rate is divided by 12 and applied monthly. Plans that compound quarterly or annually will differ slightly.
Deposits at the start of the month: if your deposits occur at the end of each month, remove the $(1 + r)$ factor from the formula and the result will be slightly lower.
Taxes and fees: the calculation is gross. Taxes on interest, account fees, or early-withdrawal penalties will reduce the actual maturity value.

To compare this plan with a lump-sum alternative, try the Term Deposit or Special Recurring Deposit calculators. If you want to know what monthly income a saved amount can generate, see the Monthly Annuity Payment calculator, or check the long-term growth rate of any investment with the Compound Annual Growth Rate (CAGR) calculator.

Frequently Asked Questions

How do I calculate the maturity value by hand?

Convert the annual rate to a monthly rate by dividing by 100 and then by 12 (6% $\to$ 0.005). Multiply the years by 12 to get $n$. Then compute $A = P \times \frac{(1+r)^n - 1}{r} \times (1+r)$, where $P$ is your monthly deposit. Subtract $P \times n$ from $A$ to find the interest earned. A scientific calculator or spreadsheet handles the exponent easily.

What happens if I deposit at the end of the month instead of the beginning?

The calculator assumes an annuity due — deposits at the start of each month, so every deposit earns one extra month of interest. If you deposit at month-end (an ordinary annuity), drop the $(1+r)$ multiplier from the formula. The result will be slightly lower; over 5 years at 6% on $500 monthly, the difference is roughly $170.

What is a good interest rate for a reinvestment or recurring deposit plan?

Rates vary widely by country and institution. Bank recurring deposits commonly pay somewhere between the local savings and fixed-term deposit rates, while dividend reinvestment plans depend entirely on market performance and are not guaranteed. A higher rate helps, but the term and your deposit discipline usually matter more. Compare offers carefully and check whether the quoted rate is fixed for the whole term.

Does the calculator account for taxes and fees?

No. The result is a gross figure: it ignores income tax on interest, account maintenance fees, and early-withdrawal penalties. Depending on your jurisdiction, interest may be taxed annually or at maturity, which reduces your net return. For a realistic estimate, subtract the expected tax and fee drag from the interest shown, or consult a tax professional for your specific situation.

What if the interest is compounded quarterly or annually instead of monthly?

This calculator divides the annual rate by 12 and compounds monthly. With quarterly compounding, interest is credited every 3 months, so monthly deposits within a quarter earn less. The difference is usually small at typical rates, but if your plan compounds quarterly or annually, use the formula with $r$ and $n$ matching that compounding interval, or use a calculator that supports that frequency.

Can I use this calculator for deposits that are not monthly?

Only with a workaround. The formula works for any fixed interval: if you deposit quarterly, divide the annual rate by 4, set $n$ to the number of quarters, and enter the quarterly deposit as the 'monthly' amount. But because the term input is in years and always multiplied by 12, you would need to convert manually — the tool itself is designed strictly for monthly deposits.

Why is my total interest lower than a friend's, even with the same deposit?

Interest depends on three things: the rate, the term, and the timing of deposits. A shorter term or slightly lower rate makes a big difference because compounding needs time to build. Skipping deposits or paying in late also reduces growth. Compare the effective rate and the exact term rather than just the deposit amount — a plan at 6% over 10 years earns far more than double the interest of the same plan over 5 years.