What it does
rateslib is a Python fixed-income analytics library for bonds, swaps, curve construction and risk sensitivities. It combines market conventions with curve calibration and instrument calculations. Home and academic educational use is free under restricted terms; business use requires a paid licence.
A rateslib study can define a curve set, calibrate it to market quotes, value an instrument and examine how that value changes when inputs move. Curve objects specify dates, interpolation and conventions; a Solver fits curve parameters to the selected calibration instruments. Instrument methods then expose outputs such as a swap rate, net present value or a bond price.
The getting-started guide explains how calendars, payment conventions and fixing data fit into the calculation. Automatic differentiation calculates first- and second-order sensitivities through the same model. Keeping the curve inputs and instrument conventions with the result makes comparisons more useful.
Install the public Python package with pip install rateslib. Precompiled wheels cover Windows, macOS and Linux; an environment without a compatible wheel needs a Rust build setup. Eligible local use does not need a hosted rateslib account.
| Licence route | Price | Scope |
|---|---|---|
| Home or academic education | Free | Eligible non-commercial educational use |
| Commercial subscription | £251 per user per year | Licensed internal business use |
| Enterprise | Quoted | Terms arranged for the organization |
Business use, including installation or evaluation by a company employee, needs the appropriate licence or an agreed evaluation arrangement. The default source-available licence is not an open-source licence: it does not allow modification, redistribution or inclusion in another library. A commercial subscription supplies a licence key and different rights. Read those rights before embedding rateslib in a business tool.
Strengths
- Connects curve calibration with instrument pricing and sensitivities
- Makes market conventions, calendars and fixing inputs configurable
- Provides precompiled Python packages for the main desktop operating systems
Watch out for
- Commercial installation or evaluation requires appropriate licensing
- The default free licence restricts modification and redistribution
Best for
- Fixed-income researchers studying curve and valuation assumptions
- Teams developing licensed bond, swap or currency analytics
Sources
- rateslib fixed-income analytics and access scope (Oct 27, 2026)
- rateslib curve, solver and instrument examples (Oct 27, 2026)
- rateslib installation, conventions and analytical controls (Oct 27, 2026)
- rateslib licences, commercial price and restrictions (Oct 27, 2026)