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Financial independence calculator

This financial independence calculator answers two questions in today's money: what target capital covers your desired monthly withdrawal over a finite horizon you choose, and how long your saving path takes to reach it. You supply every return and the inflation figure as your own assumptions, and the calculation runs entirely in your browser.

All defaults are example assumptions. The calculator works in real terms (today’s purchasing power), assumes constant real returns, uses no 4% rule and makes no claim about a "safe" withdrawal rate. Returns and inflation are your assumptions; no date is guaranteed. The calculation runs in your browser; nothing is stored.

Your target (withdrawal)

Your path there (saving)

Your assumptions (returns and inflation)

What your result means

The target capital is the capital that funds your real desired withdrawal over the finite horizon you chose. If your current wealth already exceeds it, the target is reached in the model. Otherwise the calculator shows the month in which your saving path reaches the target, or that it is not reached within 100 years. Because real markets fluctuate, that month is a model output under your assumptions rather than a date you can rely on.

How this calculator works

The calculator works in real terms: today's purchasing power. It turns each nominal return assumption into a real annual rate using your inflation figure, real = (1 + return/100) / (1 + inflation/100) − 1, and does this separately for the saving phase and the withdrawal phase. Each real annual rate then becomes an effective real monthly rate, qA and qW, through the twelfth root.

The target capital is the present value of an end-of-month annuity over m = withdrawal years × 12 months, discounted at the real withdrawal rate qW. Put plainly, it is the sum that funds your desired withdrawal in real terms across exactly that finite horizon and runs down to zero as planned. Where the real withdrawal rate is effectively zero, the target is simply the withdrawal times m. The gap is that target less your current wealth, floored at zero.

To see how long saving takes, the calculator projects your capital forward: the future value after t months of your existing wealth plus a constant real, end-of-month contribution earning the real saving rate qA. It looks for the smallest whole month t, up to 1,200 (100 years), at which that capital first meets the target. If nothing within that horizon reaches it, the calculator says so plainly instead of inventing a date. It also reports the capital you would hold after your chosen number of years, and the constant real contribution that would meet the target in exactly that time.

The model is deterministic and assumes constant real returns throughout. The withdrawal horizon is finite and entirely your choice, and the popular 4% rule is deliberately not used here. Everything the model leaves out is set out under the limitations: taxes, costs, market swings and sequence-of-returns risk.

Formula and variables

rA = (1 + iA/100) / (1 + inf/100) - 1 (real saving return)rW = (1 + iW/100) / (1 + inf/100) - 1 (real withdrawal return)qA = (1 + rA)^(1/12) - 1, qW = (1 + rW)^(1/12) - 1TC = E * (1 - (1 + qW)^(-m)) / qW, m = withdrawal years * 12FV(t) = K0*(1 + qA)^t + S*((1 + qA)^t - 1)/qAS* = (TC - K0*(1 + qA)^h) * qA / ((1 + qA)^h - 1), h = target years * 12
E
desired monthly withdrawal in today's money
iA
nominal saving return in % p.a. (your assumption)
iW
nominal withdrawal return in % p.a. (your assumption)
inf
inflation assumption in % p.a.
qA
effective real monthly rate of the saving phase
qW
effective real monthly rate of the withdrawal phase
m
number of withdrawal months = withdrawal years times 12
h
number of saving months = target years times 12
TC
required real target capital
K0
current wealth at the start
S
real monthly saving (input)
S*
saving needed to reach the target in h months

Worked examples

Example 1: target reached, 2,000 over 30 years, saving 500

Example inputs
Monthly withdrawal (today)€2,000.00
Withdrawal horizon30 years
Current wealth€0.00
Monthly saving (today)€500.00
Desired years to target15 years
Saving / withdrawal return / inflation5% / 3% / 2%
Example results
Target capital€623,949.15
Capital gap€623,949.15
Time to target576 months (48 years)
Capital after 15 years€112,603.56
Required monthly saving€2,770.56

In real terms this is a 2.9412% saving return and a 0.9804% withdrawal return. The target capital of €623,949.15 funds €2,000.00 in real terms over 360 months. At €500.00 per month the model path reaches the target only after 576 months; to reach it in the desired 15 years you would need €2,770.56 per month.

Example 2: target not reached, 5,000 over 40 years, saving 10

Example inputs
Monthly withdrawal (today)€5,000.00
Withdrawal horizon40 years
Current wealth€0.00
Monthly saving (today)€10.00
Desired years to target10 years
Saving / withdrawal return / inflation0% / 0% / 0%
Example results
Target capital€2,400,000.00
Time to targetnot reached within 100 years
Capital after 10 years€1,200.00
Required monthly saving€20,000.00

With no return and no inflation the target capital is simply €5,000.00 × 480 months = €2,400,000.00. At €10.00 per month the saving path does not reach the target within 100 years; after 10 years there is only €1,200.00. To reach the target in 10 years you would need €20,000.00 per month. The calculator states the not-reached case explicitly instead of inventing a date.

Assumptions

  • Every return and the inflation figure are your own assumptions; real markets do not deliver constant returns.
  • The calculation is real (today's purchasing power): real return = (1 + return/100) / (1 + inflation/100) − 1, separately for saving and withdrawal.
  • A constant real saving means the saving amount stays constant in today's purchasing power (end of month).
  • The target capital is the present value of an annuity over a finite withdrawal horizon you choose, and is planned to run down to zero across it.

Limitations of this calculator

  • Deterministic model: it assumes constant real returns and does not model taxes, costs, market swings, volatility or sequence-of-returns risk (no Monte Carlo simulation).
  • No safe withdrawal rate, no universal 4% rule and no capital-preservation or perpetual mode.
  • No product or investment recommendation and no guaranteed date; no default return is market truth.
  • Distinct from a withdrawal plan calculator, which tracks how an existing pot runs down month by month, and from a retirement-gap calculator, which weighs your need against the income you expect.

Frequently asked questions

Why does the calculator not use the 4% rule?

The 4% rule is a popular rule of thumb for an open-ended withdrawal, built on historical US data with many assumptions. This calculator deliberately does not use it. Instead you work with a finite withdrawal horizon you choose yourself: the target capital is the real present value of your desired withdrawal over exactly that time. That is more transparent and makes no claim about a safe rate.

What does "constant real saving" mean?

The saving amount stays constant in today's purchasing power. In tomorrow's money you would therefore pay in a little more each year to keep the purchasing power. The calculator works in real terms throughout, so target capital, gap and saving all stay comparable in today's money.

Is the date it reaches the target a guarantee?

No. The model assumes constant real returns; real markets fluctuate and deliver good and bad years in changing order (sequence-of-returns risk). The month in which the target is reached is a model output under your assumptions, not a guaranteed date.

Why two returns for saving and withdrawal?

Many people invest more aggressively while saving than in retirement. Separate return assumptions reflect that without forcing you onto a single value. Both are your assumptions; no default return is market truth.

How is this different from a withdrawal plan or retirement-gap calculator?

This calculator starts from a desired withdrawal and works out the target capital and the time to reach it. A withdrawal plan calculator does the reverse for money you already hold: it tracks how that pot runs down month by month. A retirement-gap calculator sizes the shortfall between what you will need and the income you expect. Use this one to set the target, and the others to plan around it.

Sources and further reading

Official and independent sources on this topic. The links open each website in a new tab; no content is loaded from them into this page.

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Last reviewed: 23/09/2026 · All calculations run in your browser – inputs are not stored. ·How we check our calculators