Invest Ksh 500,000 at Guaranty Trust Bank for 20 years.
At Guaranty Trust Bank's current weighted-average deposit rate of 8.01%, a Ksh 500,000 deposit grows to about Ksh 2,468,300 after 20 years — about Ksh 1,968,300 in interest, assuming monthly compounding and no withdrawals.
Final balance
Ksh 2,468,300
4.94× your deposit
Deposited
Ksh 500,000
One-off, no withdrawals
Interest earned
Ksh 1,968,300
At 8.01% p.a.
Year by year
Contributions form the floor; interest compounds on top.
Could you earn more elsewhere?
The same Ksh 500,000 in Cytonn Money Market Fund — currently Kenya's top-yielding MMF at 9.39% net of 15% WHT — would grow to about Ksh 3,246,389 over the same 20 years. Run your own numbers on the compound interest calculator.