Quantifies the interest to plead on a debt or damages claim. Choose the basis you are claiming under (s.35A Senior Courts Act 1981 in the High Court, s.69 County Courts Act 1984 in the County Court, or a contractual rate), choose a rate — a margin above the Bank of England base rate (the usual convention, applied across base-rate changes), or a fixed rate — and add each sum with the date interest runs from. The calculator returns the total interest to the calculation date, the daily rate it continues at, and a ready-to-paste pleading sentence. Statutory interest under s.35A / s.69 is simple and discretionary ("such rate as the court thinks fit"); base rate plus 1–2% is a common convention, not an entitlement.