About
Bike Geometry Calculator is a powerful, browser-based tool designed for cyclists, bike fitters, and frame geometry enthusiasts who want to accurately measure, record, and compare bike geometries and fit positions. The app allows users to calculate a full frame geometry chart from simple XY measurements, fill in sparse manufacturer geometry charts, and visually compare two bikes using a shadow bike overlay feature. Key capabilities include multiple measurement modes — Frame Geometry, Components, Bike Fit, Quick Fit, and Fit Delta — which can be toggled on and off depending on the task at hand. Editing any single measurement automatically adapts all related values, making it easy to explore how component changes affect overall riding position. The shadow bike feature is particularly useful for comparing two bikes visually, and the Fit Delta mode displays exact fit differences when the shadow bike is active. The app stores its current state in the browser URL, making it effortless to share or bookmark charts. An unlimited undo history ensures users can experiment with measurements safely without losing data. While it functions on mobile screens, it is best experienced on tablets or desktops. It is ideal for testing frame sizes before purchasing, matching fit between two bikes, or understanding how swapping components changes riding position. Importantly, this is not a body-measurement-based bike fitting tool — it focuses on mechanical geometry and fit comparison, making it a precise technical aid rather than a general fitness advisor.
Key Features
- Frame Geometry Calculation: Calculate a complete frame geometry chart from simple XY measurements or fill in gaps from sparse manufacturer geometry charts.
- Shadow Bike Comparison: Enable a shadow bike overlay to visually compare two bikes side by side and identify differences in fit and geometry.
- Multiple Measurement Modes: Toggle between Frame Geometry, Components, Bike Fit, Quick Fit, and Fit Delta modes for flexible, task-specific measurement workflows.
- URL-Based State Sharing: The current chart state is encoded in the browser URL, making it trivial to share or bookmark geometry configurations.
- Unlimited Undo History: Revert any edits or imports at any point with an unlimited undo history, allowing safe exploration of geometry changes.
Use Cases
- Cyclists evaluating frame sizes and geometry data before purchasing a new bike
- Bike fitters comparing the fit of a client's current bike against a potential replacement
- Riders calculating full frame geometry from incomplete manufacturer specification sheets
- Cyclists experimenting with how component swaps (stem length, saddle height) affect overall riding position
- Enthusiasts recording and sharing custom bike geometry setups via sharable browser URLs
Pros
- Completely Free: No account or payment required — fully accessible in any modern browser at no cost.
- Instant Sharing via URL: Charts are encoded in the browser URL, making collaboration and sharing effortless without sign-ups or exports.
- Automatic Measurement Adaptation: Editing one measurement automatically updates all related values, simplifying complex geometry calculations significantly.
- Flexible Measurement Modes: Multiple toggleable measurement sets let users focus on exactly what they need, from full geometry to quick fit comparisons.
Cons
- Not a Body-Based Fitting Tool: The app does not generate bike fit recommendations from body measurements — it is purely focused on mechanical geometry and fit comparison.
- Limited on Small Screens: While mobile-compatible, the chart interface is best experienced on tablets or desktops due to its visual complexity.
- No Account or Persistent Cloud Save: There is no user account system, so data only persists via the browser URL — losing the URL means losing the saved chart.
Frequently Asked Questions
What is the Bike Geometry Calculator used for?
It is used to calculate frame geometry, compare bike fits, test how component changes affect riding position, and visually compare two bikes side by side.
Is this tool free to use?
Yes, Bike Geometry Calculator is completely free with no account, subscription, or payment required.
How do I save or share my geometry charts?
The current state of your chart is encoded directly in the browser URL. Simply copy and share the URL to save or send your chart to others.
Can I compare two bikes at the same time?
Yes — the shadow bike feature lets you load a second bike for visual comparison, and Fit Delta mode shows the exact fit differences between the two bikes.
Is this a body-measurement bike fitting tool?
No. The app is focused on mechanical geometry and fit comparison between bikes, not on recommending fits based on a rider's body measurements.
