Is that guaranteed return actually possible?
A guarantee is a promise to pay regardless of what markets do. Somebody has to carry the loss if the money is not there. This page lines the promise up against the rates that genuinely are guaranteed, and against the best long-run records that are not.
Enter the numbers
Mathematically impossible to sustain
Compounded, this turns a small deposit into more money than exists. Nobody has ever sustained it. The advertised number is bait.
The same rate against what is actually guaranteed
Reference levels: long-run approximations, October 2026. A multiple of "-" means the comparison does not apply.
| Reference level | Rate | Your promised rate in multiples |
|---|---|---|
| Insured bank deposit (US, FDIC) | 3.5% a year (guaranteed) | more than 4.93e+10x |
| 3-month US Treasury bill | 4.0% a year (guaranteed) | more than 4.31e+10x |
| US inflation (consumer prices) | 2.5% a year (not investable, measures erosion) | more than 6.9e+10x |
| S&P 500, long-run average | 10.0% a year (not guaranteed to anyone) | more than 1.72e+10x |
| Best long-run professional record (Buffett, decades) | 20.0% a year (not guaranteed to anyone) | more than 8.62e+09x |
This rate is above every long-run reference on this page, including the best professional record ever documented. Reference levels are not targets; they are the ceiling of what has been achieved or guaranteed.
Annualised = (1 + rate) ^ periods per year - 1.
The red line
A guaranteed return higher than a Treasury bill or an insured deposit cannot exist. Every dollar paid above the risk-free rate is paid for with risk, leverage, or other people's deposits. A published promise of a fixed return above the risk-free rate is the definition of a return trap.
Reading the result
- The reference levels are the honest yardstick: two of them are guaranteed (a state-insured deposit and a short government bill), one measures erosion (inflation), and two are the best documented long-run results that are explicitly not guaranteed.
- A rate below the guaranteed levels is not automatically safe either. The question is always who is legally obliged to pay, and with what assets.
Questions this calculator answers
- What return can actually be guaranteed?In practice, the yield on a government bill held to maturity, and the rate on a deposit insured by a state scheme. Both are guarantees of the currency, and both sit near the top of the risk-free range in the table above.
- What about a fund or an insurance product promising 8%?Ask for the legal obligation. If the promise is not backed by a regulated balance sheet, it is an advertisement, not a guarantee, and the table above shows how far 8% sits above anything that can be underwritten.
- Can a company guarantee high returns legally?A licensed insurer can guarantee a contractual rate it can afford to underwrite, usually near the risk-free level. Nothing supervised guarantees a rate several times the government bill, because no underwriter can fund it.
These are arithmetic tools, not investment advice, and no calculator can tell you whether a particular operator is honest. What the arithmetic does show is whether the advertised return could come from a supervised product at all. To see the returns that are being promised in the wild, read the register, or the method and math page for how entries are built.