Divide 114 by the rate for tripling time, 144 for quadrupling.
The same logarithmic trick as the Rule of 72, extended. At 7%: double in ~10 years, triple in ~16, quadruple in ~21.
Same limitation as the Rule of 72 and worse at the extremes, because the error compounds over the longer horizon. At 2% the rule says 57 years to triple; the true figure is 55.5. Over that span inflation matters far more than the arithmetic — tripling in nominal terms may be no gain at all.
At 8% the rule says 14.25 yr and the exact answer is 14.275 yr — within half a percent. It holds to within 5% up to 19%, then drifts.
Same trick as 72, one step further out, and it drifts the same way for the same reason.
The rule against the exact answer, computed across the range. Inside the shaded band the shortcut is close enough to use; outside it, reach for the calculator.
Estimate with the rule, then check it against the calculator that models it properly.
Open Compound Interest Calculator →Divide 114 by the rate for tripling time, 144 for quadrupling. The same logarithmic trick as the Rule of 72, extended.