Sri Lanka Fixed Deposit (FD) Calculator

Every CBSL-licensed commercial and savings bank in Sri Lanka uses the same two formulas for rupee FDs — the maths is universal; only the published rate and any senior-citizen bonus differ. The calculator above applies the right formula for the chosen payout type, deducts the 5% Withholding Tax where applicable, and shows both a period-by-period accumulation table and a side-by-side bank comparison.

1. Cumulative FD (compounds monthly). The standard convention across Sri Lankan LCBs is monthly compounding, paid in a single lump at maturity: A = P × (1 + r ÷ 12)n, where P is the principal, r is the nominal annual rate, and n is the tenure in months. Source: CBSL Banking Act Direction No. 7 of 2011 §3, which mandates AER disclosure on cumulative deposits.
2. Monthly-payout FD (simple interest). Interest is paid out each month and does not compound; the principal is returned at maturity: monthly = P × (r ÷ 12); total interest = monthly × n; maturity payout = P.
3. Withholding Tax. The Inland Revenue (Amendment) Act No. 45 of 2022 imposes a 5% WHT on interest paid by financial institutions to resident individuals. The bank deducts it at credit time and remits to IRD. Net interest = gross interest × (1 − 0.05); net maturity = gross maturity − total WHT.
4. Effective annual yield (EAY). Normalises the return to a single per-annum figure so tenures and payout types are comparable: EAY = (final ÷ P)12/n − 1. The calculator reports both gross and net (post-WHT) yields.
5. Cross-check by AER (CBSL Direction 7 of 2011). The cumulative maturity is independently re-derived using the AER form A = P × (1 + AER)n/12 where AER = (1 + r ÷ 12)12 − 1. The two methods agree to the rupee — a useful credibility check that the monthly-compounding implementation is correct.
6. Senior-citizen bonus.Where a bank publishes a documented senior FD scheme (NSB Senior Citizens' Deposit, BoC Pension+ Saver, People's Senior+, and similar at the private banks), the data file stores a per-bank bonus in basis points and the calculator adds it to the standard rate when the senior toggle is on. Bonuses range from 25 to 100 basis points across the listed banks.
7. Bank comparison.For each of the eleven banks, the calculator applies the bank's published rate for your tenure (plus the senior bonus where applicable) to your principal under the same payout-type and WHT toggles you chose. Rows are sorted by net maturity descending so the highest-paying option is always at the top.

The CBSL's AWFDR (Average Weighted Fixed Deposit Rate) is the system-wide benchmark for rupee FD rates and currently sits around 9.25% as of 2026-05-10. Individual bank rates cluster within roughly ±50 basis points of AWFDR for 12-month tenures, with longer tenures usually within ±25 basis points of the bank's 12-month rate. The calculator treats every FD as a fixed-rate term deposit — no early-withdrawal penalty modelling, no premature uplift, no auto-renewal scenarios. Those edge cases are bank- and product-specific and would mislead if blended into a single number.

All three figures reconcile against a manual spreadsheet to the rupee. The calculator above derives every example from the same pure module that powers the live tool, so the rendered numbers will match these by construction.

• Central Bank of Sri Lanka — Weekly Economic Indicators (AWFDR / AWNDR)
• CBSL Banking Act Direction No. 7 of 2011 — Disclosure of Interest Rates (AER)
• Inland Revenue Department — Withholding Tax on Interest Income
• Bank of Ceylon — published FD rates
• Commercial Bank — published FD rates
• DFCC Bank — published FD rates
• Hatton National (Pension) — published FD rates
• HNB — published FD rates
• NDB Bank — published FD rates
• NSB — published FD rates
• Pan Asia Bank — published FD rates
• People's Bank — published FD rates
• Sampath Bank — published FD rates
• Seylan Bank — published FD rates

Bank rates and the CBSL AWFDR anchor were last cross-checked against each bank's published FD page on 2026-05-10. The compounding convention (monthly for cumulative, simple for monthly payout) is universal across Sri Lankan LCBs. Spotted a rate that has moved? Email me — most updates ship within 24 hours.