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Recurring Deposit Interest Calculator: Why Installment Savings Earn Less Than the Advertised Rate

A recurring deposit calculator estimates interest on a monthly savings plan, but the advertised annual rate almost never equals what you actually earn. Here's why the math works out that way.

Each monthly deposit earns interest only from the day it's made

Unlike a term deposit where the full principal earns interest from day one, a recurring deposit adds a new deposit each month, and each one only accrues interest for the months remaining until maturity, not the full term.

The last deposit barely earns any interest at all

The final monthly deposit, made at or near maturity, might only accrue interest for a single month (or none), while the first deposit earns interest for close to the full term. This is structural, not a product flaw.

The calculation sums interest across all deposits individually

Total interest is roughly the sum of (monthly deposit x annual rate x remaining months / 12) for every single deposit. For a 12-month plan, that means deposit 1 earns close to a full year of interest, while deposit 12 earns close to none.

Effective annual yield ends up well below the advertised rate

Because deposits are spread out rather than all earning interest for the full term, the effective yield on total contributions is roughly half the advertised annual rate for a simple, evenly-spread recurring deposit β€” a rough rule of thumb worth knowing before comparing products by headline rate alone.

Missed or late monthly deposits usually reduce the final payout

Most recurring deposit products require deposits on a set schedule; missing a deposit either reduces the interest-earning period for that installment or, in stricter products, can affect the account's eligibility for the full advertised rate.

Why recurring deposits and term deposits aren't directly comparable by rate alone

A term deposit's advertised rate applies to money that sits for the entire term, while a recurring deposit's advertised rate applies to money that trickles in over that same term. Comparing the two products by their headline percentage alone overstates how much the recurring deposit actually earns relative to a lump sum.

The 'half the rate' shortcut, and where it breaks down

For a recurring deposit with even monthly deposits and simple interest, effective yield on total money contributed is close to half the advertised rate, since on average each dollar deposited only earns interest for about half the total term. This shortcut gets less accurate with irregular deposit amounts, compounding structures, or bonus-rate promotions layered on top.

Frequently Asked Questions

So is a recurring deposit a bad way to save?

Not necessarily β€” it's not primarily a high-yield tool, it's a discipline tool that builds a savings habit from monthly income you don't have as a lump sum. Comparing its effective yield honestly against a lump-sum term deposit just avoids being misled by the headline rate.

Why do some recurring deposit calculators show a higher effective return than expected?

Some products offer bonus rates for meeting conditions (automatic transfers, new customer promotions, or linked accounts), or compound interest partway through the term, both of which can push the effective yield above the simple 'half the rate' estimate.