How much do I need to save per month to reach a goal?

Use a savings goal calculator with your target amount, current savings, an assumed annual rate of return, and your time horizon. It works backward from the target, compounding your current savings first, then solves for the equal monthly contribution needed to close the remaining gap.

What if I don't know what rate of return to assume?

Run the calculation at a few different rates — for example a conservative 2-3% for cash savings, or 5-7% for a diversified investment goal — and compare the required monthly contributions. A lower assumed rate always requires a larger monthly contribution to reach the same target.

Does saving for retirement use a different calculation than a regular savings goal?

The underlying math is the same backward-from-target calculation. The difference is usually the time horizon (often decades) and that a dedicated retirement calculator also models a separate current-balance compounding step, which matters more over very long periods.

What happens if my current savings already exceed my target?

The required monthly contribution is zero, or the calculation may return a negative figure indicating you have already reached the goal under the stated assumptions. Some calculators will simply cap the result at zero.

Why does starting five years earlier reduce the monthly amount needed so much?

A longer time horizon gives both your current savings and each contribution more time to compound. Because compounding accelerates over time, the required monthly contribution to reach a fixed target drops disproportionately as the time horizon extends — not just linearly.

Savings guide · Reviewed 28 August 2026

How much to save each month to reach a goal.

A savings goal calculator works backward: instead of asking what a contribution grows into, it asks what contribution is required to hit a target. Here is how that calculation works, why time horizon matters more than most people expect, and how the same math applies to a retirement target.

The backward calculation: target, current savings and time

A savings goal calculation starts with four numbers: the target amount you want to reach, your current savings, an assumed annual rate of return, and the time you have. The calculator first compounds your current savings forward across the time period on its own — that portion grows without any further contributions. Whatever gap remains between that compounded amount and your target is then converted into an equal monthly contribution using the standard annuity formula, solved for payment rather than for future value.

This is the reverse of a typical compound-growth projection. A future-value calculator asks "what does this contribution become?" A savings goal calculator asks "what contribution gets me there?" Both use the same underlying mathematics, just solved for a different variable — which is why the same current-savings and assumed-rate inputs matter in both directions.

Why the assumed rate changes the required monthly amount so much

The assumed annual rate of return is doing more work in this calculation than it might appear. A higher assumed rate means your current savings and each contribution compound faster, so a smaller monthly contribution reaches the same target. Because the effect compounds over the full time period, a modest difference in assumed rate — say 3% versus 6% — can change the required monthly figure substantially over a ten or twenty year horizon.

This is why it helps to run the calculation more than once. Test a conservative rate appropriate for cash or short-term savings, and a higher rate appropriate for a longer-term diversified goal, and compare the two required monthly contributions side by side. Treat the gap between them as the price of uncertainty in your assumption, not as a range you can average away.

Why time horizon matters more than most people expect

Because compounding accelerates over time rather than growing at a constant pace, the required monthly contribution to reach a fixed target does not shrink in a straight line as your time horizon extends — it drops faster than that. Reaching the same target in 20 years instead of 10 does not simply require half the monthly contribution; it typically requires meaningfully less than half, because both your current savings and your future contributions get many more compounding periods.

Illustrative required monthly contribution to reach the same $100,000 target — longer horizons need dramatically smaller monthly amounts.

Applying this to a retirement savings target specifically

The same backward calculation underlies "how much do I need to save for retirement" once you have a target balance in mind. The main difference from a general savings goal is the time scale: retirement horizons often run 20 to 40 years, which is exactly the range where the earlier point about compounding matters most. A retirement-specific calculator typically separates the current-balance compounding step from the contribution-series calculation more explicitly, because over such long periods that distinction has a large effect on the result.

If you do not yet have a specific retirement balance target, work backward from an assumed spending need first — a separate question from the savings-goal math covered here — then treat that number as the target you plug into a savings goal or retirement calculator. Re-run the calculation whenever your target, timeline or assumed rate changes materially, rather than treating one result as fixed for years.

Calculate your required monthly contribution ↗ Model a retirement-specific target ↗

Frequently asked questions

How much do I need to save per month to reach a goal?: Use a savings goal calculator with your target amount, current savings, an assumed annual rate of return, and your time horizon. It works backward from the target, compounding your current savings first, then solves for the equal monthly contribution needed to close the remaining gap.
What if I don't know what rate of return to assume?: Run the calculation at a few different rates — for example a conservative 2-3% for cash savings, or 5-7% for a diversified investment goal — and compare the required monthly contributions. A lower assumed rate always requires a larger monthly contribution to reach the same target.
Does saving for retirement use a different calculation than a regular savings goal?: The underlying math is the same backward-from-target calculation. The difference is usually the time horizon (often decades) and that a dedicated retirement calculator also models a separate current-balance compounding step, which matters more over very long periods.
What happens if my current savings already exceed my target?: The required monthly contribution is zero, or the calculation may return a negative figure indicating you have already reached the goal under the stated assumptions. Some calculators will simply cap the result at zero.
Why does starting five years earlier reduce the monthly amount needed so much?: A longer time horizon gives both your current savings and each contribution more time to compound. Because compounding accelerates over time, the required monthly contribution to reach a fixed target drops disproportionately as the time horizon extends — not just linearly.

Source note: This guide uses standard annuity mathematics solved for payment amount. All calculations happen in your browser — nothing you enter is sent to a server or stored. This is educational financial information, not a savings plan or personalised advice.