Calculators
The arithmetic that decides outcomes
0.75% charge, 30 years
$147k
Recover a 50% fall
+100%
US 10-year yield
5.18%
Market-implied inflation
2.33%
Same yield, after inflation
2.79%
A 10-year bond, yields +1
-7.4%
8% average, varying 60%
-10.2%
Rule of 72
7.2%
What it costs you
Fee drag
What do charges actually cost?
A percentage a year sounds small. Compounded across a working life, and including the growth the fee itself would have earned, it usually costs more than most people expect.
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Real returns
What is a return worth after inflation?
Headline yields are quoted before inflation, which is not what you keep. The inflation assumption starts at the rate the Treasury market is pricing today rather than a number you have to invent.
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Volatility drag
Why is an average return not what you get?
Up 50% then down 50% averages zero and leaves you down a quarter. The variability presets are measured from a year of real closing prices, so the effect scales from negligible to severe on its own.
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What it does to you
Drawdown recovery
How much do you need to get back?
A fall and the gain that undoes it are not the same number, because the gain is calculated on what is left. Lose half and you need to double.
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Bond price sensitivity
What does a yield move do to a bond?
A government bond can lose a fifth of its value without the issuer missing a payment. Seeded with the live curve from six government bond markets, and computed from the bond's own cash flows.
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What actually happened
Regular investing
How did buying monthly actually do?
Run monthly contributions against the real price history of an index, a metal or a cryptoasset, and compare it against committing the same money on day one.
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Blend two holdings
Does mixing two things beat holding one?
A weighted mix run against real history and rebalanced at an interval you choose, against the return and variability of holding either on its own.
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What each charge level costs
$50,000 plus $500 a month, 7% for 30 yearsA large index tracker · 1% of the fee-free outcome
Typical platform charge · 5% of the fee-free outcome
Active fund · 15% of the fee-free outcome
Advised, with a platform on top · 28% of the fee-free outcome
Advised and actively managed · 35% of the fee-free outcome
Identical inputs throughout, so the only difference is the charge. Change the assumptions
What a fall requires
And how long at 7% a year| Fall | Gain needed | Years at 7% |
|---|---|---|
| −10% | +11% | 1.6 |
| −20% | +25% | 3.3 |
| −30% | +43% | 5.3 |
| −40% | +67% | 7.6 |
| −50% | +100% | 10.2 |
| −60% | +150% | 13.5 |
| −80% | +400% | 23.8 |
The gain is always larger than the fall, because it is calculated on the smaller amount that remains. Try your own figures
Live inputs
What seeds these calculatorsTen-year government yields, each from its own central bank or finance ministry. Full curves
How long money takes to double
Exactly, rather than by the rule of 72| Annual return | Years to double | 72 divided by rate |
|---|---|---|
| 2.0% | 35.0 | 36.0 |
| 4.0% | 17.7 | 18.0 |
| 6.0% | 11.9 | 12.0 |
| 8.0% | 9.0 | 9.0 |
| 10.0% | 7.3 | 7.2 |
| 12.0% | 6.1 | 6.0 |
The familiar shortcut is accurate near 8% and drifts either side of it. At the US ten-year yield of 5.18%, money doubles in 13.7 years before inflation and 25.2 years after it.
Why these seven
Most investing content is about what to buy. These are about the things that decide the outcome regardless of what you buy: what you are charged, what inflation takes, what a loss requires to undo, what a rate move does to a bond you already hold, what variability quietly costs, and what regular contributions and mixing do.
Every calculator states its assumptions underneath the result. Where a figure is our arithmetic rather than a published statistic, it says so. None of this is advice or a recommendation, and none of it forecasts what any investment will do next.
The one thing worth internalising
All seven describe the same asymmetry from different angles. Percentages are not symmetric once money compounds: a loss needs a larger gain to undo it, a charge removes both the fee and everything it would have earned, and variability alone leaves you behind a steady return with the identical average.
None of this depends on being right about markets. It applies whatever you hold, which is why it is worth more attention than the choice of holding usually receives.