Simulation
Watts the Difference: Cycling Performance Calculator
A physics-based web calculator that quantifies the speed and watt impact of common marginal gains in cycling — from body weight and position to tyre pressure, chainring size and atmospheric conditions — built with ex-pro cyclist Viktor Verschaeve.
Links & Resources
The Question Every Cyclist Asks
Hit race weight or add ten watts to your FTP? Ride in the drops or buy an aero frame? Switch to tubeless tyres or spend those hours on training instead? The marginal gains conversation in cycling is everywhere, but quantitative answers are hard to come by without access to a wind tunnel or a physics-based simulation tool.
Watts the Difference is a public web calculator that makes these comparisons accessible. Enter a route — or use one of the preset scenarios — specify your current setup and the change you are considering, and the calculator returns the predicted time saving and equivalent watt difference under realistic conditions.
What It Models
The calculator covers the primary performance determinants in road cycling: aerodynamic drag from rider position and equipment, rolling resistance from tyre width and pressure, drivetrain efficiency, gravitational resistance on climbs and descents, and the interaction between these through pacing strategy.
The underlying model is distilled from internal simulation tooling and measurement data, reduced to first-order approximations that are fast to evaluate while capturing the dominant physics. Compute-heavy features that would not substantially change the output — grip-limited cornering, detailed fatigue dynamics, full pacing optimization — are deliberately excluded to keep the tool lightweight and freely accessible.
Collaboration
The calculator was built together with Viktor Verschaeve, a former professional cyclist and innovation coach at the Lotto Cycling Team. That collaboration ensured that the physical model was paired with practical knowledge of how cyclists actually train and race — which parameters they can realistically change, and which "optimizations" rarely translate from theory to the road.
What It Answers
The calculator is designed for "what if" exploration: what if the wind shifted, what if the route had 200 extra meters of elevation, what if the rider dropped 3 kg of body weight. It is fast enough to answer these questions in real time on a standard browser, making it a practical tool for both training planning and race-day decision making.