Monthly deposit for a savings goal:
working back from the target

Start from the target, not the deposit

Most savings plans start from what a person can afford each month and see where it leads. A goal-based plan flips that: choose the amount you need and the date you need it by, then calculate the monthly deposit that gets you there. If the answer is more than you can afford, you have learned that early enough to change the date, the amount or the return you are aiming for.

The calculation treats each deposit as earning returns from the day it goes in until the target date. Early deposits therefore do more work than later ones, which is why the answer is below the target divided by the number of months.

The deposit formula

If the rate is zero, the formula collapses to FV ÷ n, which is simply the target split into equal pieces. Any positive rate lowers the required deposit, because growth carries part of the load.

If you already have a lump sum, subtract its grown value, PV × (1 + r)ⁿ, from the target before using the formula. The remainder is what monthly deposits must cover.

Worked example: ₹10,00,000 in 5 years

Deposits made at the start of each month earn a month more, so the needed amount falls to ₹13,887, about ₹81 less.

Without any return the plan needs ₹16,667 a month, so a 7% rate cuts the monthly burden by about 16%. That is meaningful but far from decisive.

What moves the deposit more: the rate or the time

Savers often search for a higher return when the real lever is time. The table holds the target at ₹10,00,000 and varies one input at a time.

Moving the rate by a full percentage point changes the deposit by about ₹360. Doubling the horizon from five to ten years cuts it by more than half, from ₹13,968 to ₹5,778. Starting earlier is almost always a bigger win than chasing a slightly higher return.

Turning it around: how long does a fixed deposit take?

If the monthly amount is fixed by your budget and the unknown is the time, solve for n instead: n = ln(1 + FV × r ÷ deposit) ÷ ln(1 + r). With ₹10,000 a month at 7% a year the target of ₹10,00,000 is reached after about 79 months, or 6.6 years.

After five years of those ₹10,000 deposits the balance is ₹7,15,929, which is short of target by about ₹2.84 lakh. The final 19 months are where compounding finally pulls ahead: they add ₹2.84 lakh on deposits of only ₹1.9 lakh.

An alternative to a larger flat deposit is a yearly step-up. Beginning with ₹11,592 a month and raising it by 10% each year reaches the same ₹10,00,000 in five years, finishing at ₹16,973 a month in year five. That suits people whose income is rising, and it eases the early years without lengthening the plan.

Adjusting the plan for real life

• Seed lump sum: with ₹1,00,000 already saved, the monthly deposit for the same goal at 7% falls to about ₹11,988.
• Inflation: if the target is in today's money, inflate it first. A ₹10,00,000 goal in today's terms at 6% inflation becomes about ₹13,38,226 in five years, and the deposit rises to roughly ₹18,690.
• Step-ups: raising the deposit by a fixed percentage each year reduces the first-year burden but needs discipline.
• Risk: a return of 7% is an assumption. A safer plan uses a conservative rate for short goals, because there is little time to recover from a bad year.

It also helps to keep the plan flexible. Review it once a year: if the balance is ahead of the schedule, you can trim the deposit or finish early; if behind, a small top-up now costs far less than a large one in the final year, because every extra deposit has more months to grow the earlier it is made.

Common slips that throw the deposit off

• Using the annual rate as the monthly rate: 7% a month instead of 0.5833% gives a nonsensical, tiny deposit.
• Counting years instead of months: n must be the number of deposits, so 60 for five years of monthly saving.
• Treating a yearly deposit as monthly: saving once a year at 7% needs ₹1,73,891 a year, equal to ₹14,491 a month, because each rupee waits longer to start earning.
• Ignoring the end-or-start-of-month difference when comparing quotes from two providers.
• Forgetting tax or charges on the return, which lower the effective rate.

The yearly-deposit figure is a useful reminder. The same ₹10,00,000 in five years costs about ₹523 more per month if you wait until each year's end to deposit, because the early money has less time to grow.

When the number misleads

The formula assumes a constant return and equal deposits. Market-linked investments do not behave that way, and the order of good and bad years matters most near the end. If the goal date is fixed, such as a tuition payment, many savers shift gradually toward lower-risk holdings as the date approaches.

Check whether the account compounds monthly or quarterly, whether charges are deducted, and whether tax applies on maturity. A calculator is the fastest way to test these alternatives side by side.