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$1,000 invested for 20 years at 8%
Exact compound math for the given inputs.
$4,926.80
future value (monthly compounding, no deposits)
Principal$1,000.00
Interest earned$3,926.80
Growth multiple4.93×
Rule of 729.0 yrs to double
Frequently asked questions
How much will $1,000 be worth in 20 years at 8%?
With monthly compounding it grows to $4,926.80 — that is $3,926.80 of interest earned on $1,000.00.
What if compounding is annual instead of monthly?
Annual compounding gives $4,660.96 — more frequent compounding always yields slightly more.
How long until it doubles?
The Rule of 72 estimates 9.0 years at 8% (9.00 precisely).
Try nearby scenarios
Change the numbers yourself
Open the interactive compound interest calculator — every field is editable.