How to Calculate the Monthly SIP Needed for a Goal

Work back from the goal

A goal-based SIP calculation starts with the amount you want at a future checkpoint. It uses your opening balance, horizon and return assumption to solve for a fixed monthly payment.

Target, opening balance and payment

A SIP goal projection estimates the fixed monthly amount required to reach a supplied target. The target is a future amount. The opening balance is invested at the start of the model.

The funding gap is the target less the modeled opening balance at the horizon, floored at zero. The payment must fund that remaining gap under the supplied growth assumption.

Test a funding assumption

Hold the target and opening amount steady and try a zero or negative rate. Compare the required monthly payments to see how sensitive the plan is to the assumption.

SIP goal formula

Let f = (1 + A)^(1/12) for effective annual decimal return A. Grow opening balance P to P × f^n after n months. Divide a positive gap by the sum of f^k across payments. End timing uses exponents 0 through n−1, and beginning timing uses 1 through n.

Monthly requirement = max(target − P × f^n, 0) ÷ Σ f^k

Check a three-month target

With target 200, opening balance 100, three months and zero return, the gap is 100 and the mathematical requirement is 100/3 per month. Paying 33.33 ends at 199.99. Paying 33.34 ends at 200.02, a surplus of 0.02.

1. Enter 200 as target and 100 as the opening balance.
2. Enter zero annual return and three complete months.
3. Check the 33.34 payment and ending value of 200.02.

Read the funding gap before the payment

If the grown opening balance meets the target, no monthly payment is required. If it falls short and no months remain, the goal is unreachable in this model. For a positive gap and horizon, compare the mathematical amount and the upward-rounded payment.

An opening balance of 100 can be above a target of 95 today. If the opening amount shrinks to 90 by the valuation checkpoint, it still leaves a modeled gap of 5.

Enter a future target and choose timing

Enter the target, opening balance, effective annual percentage and whole months. Choose beginning or end timing. Review the opening balance at the horizon, the gap and the ending value with the rounded amount.

Use one currency for the target, opening balance and payment. The market selector changes formatting only.

Choose an inverse or forward model

Use the SIP Calculator to project a known recurring payment, or the Lump Sum Mutual Fund Calculator for a one-time investment. Use this tool to solve the fixed payment from the target.

Make the monthly checkpoints explicit

The opening balance grows for the entire horizon. Contributions are fixed and use equal model months. The final end-of-month payment receives no growth and the final beginning payment receives one month.

Beginning timing adds one period of exposure for each payment. That raises its terminal value under a positive return and lowers it under a negative return.

Understand the numerical and scenario limits

Target and opening balance must be from 0 through 10^12. Use 0 through 1,200 whole months and an annual effective rate above −100% through 100%. Decimals support 12 fractional places. The model rejects unresolved rounding thresholds, payments above 10^12 and ending balances above 10^30.

The mathematical requirement is shown to 16 significant digits. The rounded amount is verified before display rounding. Model months do not represent actual payment dates.

Avoid an unintentional shortfall

Do not compare the goal with the opening balance today when the balance has time to grow or lose value. Do not use ordinary rounding for a payment that must reach the target.

Keep an assumed effective annual rate separate from nominal APR. Estimate any desired inflation adjustment outside the model before supplying the target.

Use the same convention in five currencies

In India users often search for a SIP instalment or target corpus. In the USA and Canada, monthly contribution or savings goal can describe the same question. In the UK and Australia, a savings deadline or goal is familiar wording. Choose USD, GBP, CAD, AUD or INR.

Educational scope

Educational constant-return model. It excludes actual fund prices, dates, fees, taxes, FX and inflation. It does not forecast investment performance or guarantee the target.

Frequently asked questions

Sources and review

Sources reviewed Nov 10, 2026. Consult current local rules before relying on time-sensitive information.

• Zerodha Goal SIP explanation
• Investor.gov savings goal calculator
• MoneyHelper savings calculator
• Canadian financial toolkit
• ASIC savings goals calculator