GeraCash / UK Loan Cost Context / Methodology
Gera Borrowing Cost Index (GBCI) — Methodology
Full reproducible formula behind the Gera Borrowing Cost Index (GBCI), computed only from Bank of England published effective interest rates and the Official Bank Rate (Open Government Licence v3.0). Generic context only — never quotes any specific lender's product.
What is the Gera Borrowing Cost Index (GBCI)?
The Gera Borrowing Cost Index (GBCI) is a Gera-computed signal expressing how expensive UK lending rates are relative to the Bank of England's policy rate (the Bank Rate). It is normalised to a 0–100 scale:
GBCI = ((effectiveRate − bankRate) / bankRate) × 50 + 50Interpretation:
- · GBCI = 50 → spread exactly equals the Bank Rate (spread = 100% of bank rate)
- · GBCI > 50 → lending rates are proportionally wider above the Bank Rate
- · GBCI < 50 → lending rates are proportionally narrower above the Bank Rate
The GBCI is a generic context signal — it shows the aggregate market position, not any individual lender's rate or any prediction of what you will be offered. It is never used to imply a specific commercial APR.
Step 1 — BoE effective lending rates
Source: Bank of England Money and Credit Statistics, April 2026. Published monthly; Open Government Licence v3.0. These are aggregate effective rates across all UK monetary financial institutions — not any specific lender's product.
| Loan type | Effective rate (April 2026) | BoE series description |
|---|---|---|
| New personal loans | 9.53% | Effective rate on new personal loans to individuals |
| Newly drawn mortgages | 4.08% | Effective rate on newly drawn mortgages |
| Outstanding mortgage stock | 3.92% | Effective rate on outstanding mortgage stock |
| Interest-charging credit cards | 21.20% | Effective rate on interest-charging credit card balances |
| Arranged overdrafts | 21.79% | Effective rate on arranged overdrafts |
Step 2 — Official Bank Rate
Source: Bank of England Official Bank Rate History (OGL v3.0). The Bank Rate is set by the Monetary Policy Committee and is the base from which commercial lenders set their own rates.
| Date | Rate |
|---|---|
| 18 Dec 2025 ← current | 3.75% |
| 07 Aug 2025 | 4.00% |
| 08 May 2025 | 4.25% |
| 06 Feb 2025 | 4.50% |
| 07 Nov 2024 | 4.75% |
| 01 Aug 2024 | 5.00% |
| 03 Aug 2023 | 5.25% |
| 22 Jun 2023 | 5.00% |
| 11 May 2023 | 4.50% |
| 23 Mar 2023 | 4.25% |
| 02 Feb 2023 | 4.00% |
| 15 Dec 2022 | 3.50% |
| 03 Nov 2022 | 3.00% |
| 22 Sep 2022 | 2.25% |
| 04 Aug 2022 | 1.75% |
Step 3 & 4 — Spread and GBCI
Spread = effectiveRate − bankRate. GBCI = (spread / bankRate) × 50 + 50. Worked examples for April 2026:
| Loan type | Effective rate | Bank Rate | Spread | GBCI |
|---|---|---|---|---|
| Personal Loan | 9.53% | 3.75% | 5.78% | 127/100 |
| Mortgage | 4.08% | 3.75% | 0.33% | 54/100 |
| Credit Card | 21.20% | 3.75% | 17.45% | 283/100 |
| Arranged Overdraft | 21.79% | 3.75% | 18.04% | 291/100 |
Step 5 — Indicative total cost of credit
Standard annuity formula for equal monthly repayments:
monthlyRate = effectiveRatePct / 100 / 12
monthlyPayment = P × r × (1+r)ⁿ / ((1+r)ⁿ − 1)
totalRepayable = monthlyPayment × n
totalInterest = totalRepayable − PWorked example (personal loan £10,000, 36 months, rate 9.53%):
P = 10000
n = 36
monthlyPayment ≈ £320.47
totalRepayable ≈ £11,536.91
totalInterest ≈ £1,536.91
What GBCI does not represent
- –Any specific commercial lender's APR or product offer
- –The rate you will be offered — your rate depends on creditworthiness, income, and individual lender criteria
- –Advice to borrow or recommendations about any product
- –The total cost including arrangement fees, early repayment charges or other product-specific charges
- –Any forecast or prediction of future interest rates
- –Any endorsement of any lending product or institution
The GBCI and all cost-context figures are derived from Bank of England published aggregate statistics under the Open Government Licence v3.0. They are provided for informational context only. Always obtain a personalised quote from a regulated lender before making any borrowing decision.
Licence and attribution
Contains public sector information published by Bank of England and licensed under the Open Government Licence v3.0. Source: Bank of England — Official Bank Rate History (June 2026, published 18 December 2025).
Contains public sector information published by Bank of England and licensed under the Open Government Licence v3.0. Source: Bank of England — Money and Credit Statistics, April 2026 (April 2026, published June 2026).
The GBCI formula and indicative cost computations are original work by Gera Systems Ltd. The underlying effective rate data is Crown copyright, published by the Bank of England under the Open Government Licence v3.0. Last updated: 2026-06-20.