How much should I save each month?

The common guideline is 20% of after-tax income, but the honest answer is: whatever you will actually sustain. A $500 deposit kept up for ten years at 5% produces $77,641 from the deposits alone and another $15,876 in interest. A $1,000 deposit kept up for five months and then abandoned produces $5,000 and nothing else.

What rate should I enter?

The rate your account actually pays right now — the APY, not the APR, though at monthly compounding the difference is small. High-yield savings accounts sit around 4–5% as of mid-2026; regular savings accounts pay a fraction of one percent. If you are projecting over many years, remember the rate will change.

Is this the same as compound interest?

Yes, with the compounding locked to monthly and no inflation adjustment. If you want to change the compounding frequency or see the balance in today's purchasing power, the compound interest calculator does both.

Money

Savings Calculator

Enter what you start with, what you add each month, the rate, and how long. The rest follows.

The link carries your figures, so it reopens on exactly these numbers.

When interest overtakes your deposits

Over 10 years the interest never overtakes your deposits. Raise the rate or extend the term and it will.

What a different rate would mean

Savings rates move. One point higher or lower, on the same deposits, changes the outcome by this much.

One point lower
$81,079.07
at 4% · $16,079 interest
At the rate you entered
$85,876.19
at 5% · $20,876 interest
One point higher
$91,036.66
at 6% · $26,037 interest

The large figure is the total savings; the smaller one is the interest inside it.

How the balance builds

Scale tops out at $85,876

Year 1Year 10

Interest earnedWhat you deposited

Year by year

Each year: total deposited, interest earned, and the balance
Year	Deposited	Interest	Balance
1	$11,000	$395	$11,395
2	$17,000	$1,118	$18,118
3	$23,000	$2,184	$25,184
4	$29,000	$3,612	$32,612
5	$35,000	$5,420	$40,420
6	$41,000	$7,627	$48,627
7	$47,000	$10,255	$57,255
8	$53,000	$13,323	$66,323
9	$59,000	$16,856	$75,856
10	$65,000	$20,876	$85,876

The formula

r = annual rate ÷ 100 ÷ 12 (monthly compounding)

Each month: balance = previous × (1 + r) + deposit

After n months the balance is the sum of every deposit grown at r for the months it had left.

Worked example

$5,000 starting balance, $500 added every month, 5% annual rate, 10 years

r = 0.05 ÷ 12 ≈ 0.004167 per month
The $5,000 alone becomes $8,235 over 120 months
The $500 a month becomes $77,641
Total $85,876 — on $65,000 deposited

Where this goes wrong

Forgetting that savings rates are not fixed

A high-yield savings account quoting 5% today is not a 10-year contract. The rate moves with the central bank, and a projection at today's rate over a decade is a scenario, not a forecast. Over the last twenty years, US savings rates have ranged from near zero to above five percent. The calculator shows one rate; reality will deliver a sequence of different ones, and no one knows which.

Questions

How much should I save each month?: The common guideline is 20% of after-tax income, but the honest answer is: whatever you will actually sustain. A $500 deposit kept up for ten years at 5% produces $77,641 from the deposits alone and another $15,876 in interest. A $1,000 deposit kept up for five months and then abandoned produces $5,000 and nothing else.
What rate should I enter?: The rate your account actually pays right now — the APY, not the APR, though at monthly compounding the difference is small. High-yield savings accounts sit around 4–5% as of mid-2026; regular savings accounts pay a fraction of one percent. If you are projecting over many years, remember the rate will change.
Is this the same as compound interest?: Yes, with the compounding locked to monthly and no inflation adjustment. If you want to change the compounding frequency or see the balance in today's purchasing power, the compound interest calculator does both.