How Much Should I Save Each Month?

The number most people work out is too high

Ten thousand dollars in two years. A thousand already in the account. Divide what's left by the months and you get $375 a month — and then you look at your budget and decide the goal isn't realistic.

But $375 is the wrong number. It's what the goal costs if the money sits somewhere that pays nothing. In an account paying 4%, the real figure is $357.49, because your balance is working alongside you the whole time.

That's not a huge difference on one month. Over the two years it's the entire reason the goal lands on time.

The arithmetic

A $10,000 goal, $1,000 already saved, 24 months, at 4% a year.

Step one — the money you already have keeps earning. It's in the account for the whole 24 months, so it grows:

$1,000 × (1 + 0.04 ÷ 12)²⁴ = $1,083.14

Step two — that leaves the shortfall your deposits have to cover:

$10,000 − $1,083.14 = $8,916.86

Step three — but the deposits earn too. Not all equally: the first one compounds for nearly the whole two years, the last one arrives on the final day and earns nothing. The annuity formula handles that in one step:

$8,916.86 × 0.003333 ÷ ((1.003333)²⁴ − 1) = $357.49 a month

Where the difference actually goes

Here's the part worth seeing laid out, because the two figures are the same fact told twice.

With no interest	$375.00 a month
At 4%	$357.49 a month
Difference	$17.51 a month

Over 24 months you deposit $8,579.78 instead of $9,000. That's $420.22 less of your own money — and $420.22 is exactly the interest figure the calculator reports.

It isn't a coincidence and it isn't two separate benefits. The interest earned is the amount you didn't have to fund. Every "interest earned" number on every savings calculator is really an answer to "how much of this did I get for free?"

Why the rate matters less than you'd hope

Run the rate up and down and the shape becomes obvious:

Rate	Per month	Interest does
0%	$375.00	$0
2%	$366.20	$211.30
4%	$357.49	$420.22
8%	$340.38	$830.91

Doubling the rate from 4% to 8% saves you $17.11 a month. Real, worth having, and nowhere near the difference between saving and not saving.

Over two years, contributions dominate. Interest is a rounding error compared to the habit. This flips as the horizon stretches — over thirty years, compounding is the whole story — but for a goal you can see from here, the account you choose matters far less than the standing order you set up.

Chase the rate anyway. Just don't wait to find the perfect account before starting.

When you should ignore all of this

Put 0 in the rate box if:

• The money is in your current account, where it belongs if you need it inside a year
• You genuinely don't know the rate — guessing high is how people arrive at the deadline short
• It's an emergency fund, where instant access beats a quarter of a percent

The calculator handles zero properly. It switches to plain division rather than dividing by zero, and the number it gives you is the honest one.

Two things the calculator doesn't model

Tax. Interest on savings is taxable income in most places unless the account is sheltered. Treat the $420.22 as a gross figure. If yours is taxed, enter the rate net of tax and the plan stays safe.

A rate that moves. The maths assumes one fixed rate for 24 months. If your rate is variable and it drops, the shortfall doesn't vanish — it gets made up by your deposits instead of the bank's. Re-run this twice a year and adjust the standing order.

The bit that decides whether it works

None of the arithmetic above is the hard part. The hard part is the order you do things in.

Saving what's left at the end of the month almost never happens, because there's rarely anything left. Move the money the day after payday and live on the rest. The whole point of working out $357.49 rather than guessing is that you now know the rest is enough.

And if you miss a month — and you will — don't restart the plan or double up. Put your actual balance and your actual remaining months back into the calculator. The new number will be slightly higher, and it will be true.

Print the savings goal tracker and keep it where you'll see it.

Not financial advice — general information to help you plan. Rates, tax treatment and account terms vary.