Banks and forex bureaus add their own margin on top of the interbank mid-market rate shown here, so their buy and sell rates are always a bit worse than what this calculator shows. Use this as a reference point, then compare against your specific provider.
How often does the exchange rate change?
Continuously. The Kenyan Shilling trades against major currencies throughout the day based on market supply and demand, so any single rate is only a snapshot. You can edit the rate field here if you have a more current figure.
Who sets the official KES exchange rate?
The Central Bank of Kenya does not set the rate; it publishes a daily indicative rate calculated as the weighted average of registered interbank trades. Individual banks and forex bureaus set their own retail rates.