Treasury Bill Calculator Kenya: How to Work Out Your T-Bill Interest (November 2026 Rates)

Updated 31 October 2026

To use a Treasury bills Kenya interest rate calculator, you need three numbers: the amount you want back at maturity (the face value), the rate from the latest Central Bank of Kenya (CBK) auction, and the number of days. Treasury bills are sold at a discount: you pay less than the face value today and receive the full face value when the bill matures. The difference is your interest, from which 15% withholding tax is deducted. At the October 29, 2026 auction, the 91-day bill averaged 8.7498%, the 182-day 8.8508% and the 364-day 9.0288%, according to CBK results reported on October 30.

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The Treasury bills Kenya interest rate formula

CBK prices T-bills on a 364-day year:

Price paid = Face value ÷ (1 + rate × days ÷ 364)

Interest = Face value − Price paid

Net interest = Interest × 0.85 (after 15% withholding tax)

The rate is written as a decimal, so 8.7498% becomes 0.087498.

Worked examples: KSh100,000 face value

For a larger example: a KSh1 million 364-day bill at 9.0288% costs about KSh917,189. You receive KSh1 million after a year, a gross gain of about KSh82,811 and roughly KSh70,389 after tax.

Your actual price may differ slightly because CBK calculates it to more decimal places and because competitive bidders get the rate they bid, not the average.

Step by step: calculate your own

1. Pick the face value, the amount you want at maturity. The minimum for non-competitive bids is KSh50,000.
2. Check the latest auction rate on CBK’s website or our weekly Treasury bill rates update.
3. Multiply the rate by the days and divide by 364. For 91 days at 8.7498%: 0.087498 × 91 ÷ 364 = 0.0218745.
4. Add 1 and divide the face value by the result: 100,000 ÷ 1.0218745 = 97,859.
5. Subtract the price from the face value for gross interest, then multiply by 0.85 for net interest.

Competitive and non-competitive bids

• Non-competitive: from KSh50,000 up to KSh50 million per tenor; you get the weighted average rate. Best for most individuals.
• Competitive: from KSh2 million; you state the rate you want, and CBK may reject bids priced too high.

Bids are made through DhowCSD or Treasury Mobile Direct. The next auction, for bills dated November 9, 2026, closes at 2pm on Thursday, November 5. Our guide on how to buy Treasury bills walks through opening a CSD account.

Rolling over and planning cash flow

When a bill matures, the face value is paid into the bank account linked to your CSD account. You can then bid again in a new auction, which is called rolling over. Because rates change every week, your next bill may earn more or less than the last one. Many savers build a ladder by buying bills of different tenors, or by buying a 91-day bill every few weeks, so that some money matures regularly and is available for school fees, rent or emergencies without breaking an investment early.

Remember that you must pay the full price upfront by the settlement deadline, usually by RTGS transfer, and that CBK can accept only part of your bid when demand is high. In the October 29 auction, the 91-day bill was heavily oversubscribed while the 182-day and 364-day bills were undersubscribed, which affects how much CBK accepts at each tenor.

How T-bills compare

At about 7.4%–7.7% net, T-bills currently beat most big-bank fixed deposits; see our fixed deposit rates comparison. Treasury bonds pay more for longer terms but carry price risk if you sell early; read Treasury bills vs bonds.

FAQ

How do I calculate Treasury bill interest in Kenya?

Divide the face value by (1 + rate × days ÷ 364) to get the price, subtract it from the face value for interest, then deduct 15% tax.

What is the current 364-day T-bill rate?

9.0288% at the October 29, 2026 auction.

Is T-bill interest taxed?

Yes, at 15% withholding tax, deducted at source.

Updated October 2026.