A circuit designer built for people who actually think about racing.

What is it?

RaceTrackDesigner is a free, browser-based application built for motorsport fans, sim-racing designers, and anyone who has ever looked at a stretch of road and wondered if it could be a race circuit. You place waypoints on a live map — as a closed circuit or a rally-style point-to-point stage — and the application draws a smooth track through them, then analyses it to produce lap or stage time estimates, ten-band speed zones, a character rating, and a full engineering-style report. Two human classes even turn it into a marathon and triathlon route planner.

The tool opens on Monaco by default, and every Grand Prix on the current F1 calendar is available as a preset in the location picker. You can also search for any city, address, or place, or start from your device's current location — anywhere on Earth is fair game.

How does the circuit drawing work?

When you place waypoints, the track between them is drawn as a smooth Catmull-Rom curve rather than straight lines. The application respects the direction of approach into each waypoint, so the resulting circuit flows naturally without sharp kinks at each point. If you want a particular section to be perfectly straight — a pit straight or a Mulsanne-style runway — straight line mode is available from the Tools menu.

Every waypoint can be dragged in real time after placement. The track shape and all statistics update immediately as you drag. You can also double-click any waypoint to remove it, or undo up to 30 steps using Z or Ctrl+Z.

The track renders in two states. Before the design is complete, it shows in a neutral tone. Once you press C to complete the loop — or the stage — the track switches to the speed zone colour system: ten bands running from red for flat-out sections through orange and yellow down to green for the slowest corners.

Shaping the tarmac

The default track is 8 metres wide with 7 metres of runoff on each side, but every part of the geometry is editable. Each segment between two waypoints can have its own track width — and the left and right sides of the tarmac can be set independently, so you can model the asymmetric widening that real circuits use to encourage overtaking on the inside of a corner. Blue handles on the map let you drag widths directly; the Tools menu opens a full panel for numeric input on every segment.

Kerbs can be placed along corners and chicanes from the Tools menu — useful for visualising apex placement and exit lines. The pit lane is drawn separately alongside the main track and can be toggled on and off independently. Beyond the automatic runoff that follows the tarmac, the Run-off Painter lets you draw fully custom tarmac or gravel shapes anywhere on the map, the Building Painter adds grandstands and paddock buildings, and a measurement tool reports the exact distance between any two points.

Turn labels (T1, T2, T3…) appear automatically at every detected apex once the loop is closed. If the automatic placement doesn't match what you want — say, you want "Eau Rouge" to label a sequence rather than a single corner — custom turn labels let you manually define where a turn starts and ends and give it any name.

How does the physics model work?

The model measures the curvature of the track at every point and derives a maximum cornering speed based on the grip and downforce characteristics of the selected vehicle class. Tighter corners produce lower speed limits; sweeping curves allow much higher speeds.

Once corner speeds are established, the model applies the acceleration and braking capabilities of the car to build a continuous speed profile across the full lap. This gives you realistic top speeds, minimum speeds, and a lap time that accounts for how long it actually takes to slow down and accelerate back out of each corner.

Lap time and race laps are calculated from this profile. The results are approximations rather than a full simulation, but they are grounded in real vehicle physics and produce numbers that feel right to anyone familiar with motorsport.

The racing classes

Each class has a distinct set of performance characteristics. Switching between them on the same circuit is one of the most revealing things you can do — tight corners that barely register for an F1 car become significant obstacles in GT3, and corners that GT3 handles comfortably can be genuinely slow on a kart.

Formula 1 generates extreme levels of aerodynamic downforce that increase with speed. This means F1 actually corners more efficiently at higher speeds, producing a non-linear relationship between corner radius and minimum speed. The class is configured around a 305 km race distance, matching the minimum FIA Formula 1 distance.

GT3 represents a more accessible category derived from production road cars. It produces less downforce and lower lateral grip than F1, which makes medium-speed corners noticeably slower and gives the class a different rhythm through the same layout. Race distance is set to 100 km.

MotoGP has among the lowest cornering grip of any class, reflecting the physics of a motorcycle versus a four-wheeled car through the same corner. Despite this, the extraordinary power-to-mass ratio of a MotoGP machine means it matches F1 for top speed on long straights. Race distance is 110 km.

IndyCar is open-wheel racing built for both ovals and road courses. The model is less downforce-dependent than F1 and has a flatter cornering profile, which makes it rewarding on entirely different layouts — high-speed ovals where minimum speed barely drops, or tight street circuits where braking points decide everything. Race distance is 805 km — the full Indy 500.

NASCAR represents heavy stock cars — 1,540 kg of metal with 500 kW under the hood and a 290 km/h top end. Lower cornering grip than the open-wheel classes and a much higher mass produce braking zones that demand respect, with a 400 km race distance reflecting the real-world endurance of stock car racing.

Go Kart uses a 180 kg shifter kart with 22 kW and no aero to speak of. The speed range is smaller — 130 km/h top speed — but the differences between corners are sharper, which is why the speed zone thresholds are scaled down specifically for kart-scale racing. Use it to lay out kart circuits at their natural size, with a 15 km race distance.

WRC is the rally car — 1,260 kg, all-wheel drive, and 280 kW, tuned for 25 km point-to-point stages and selected automatically when you choose one. It is also the only motorsport class with per-segment surfaces: mark a section as dirt and the model cuts cornering grip, traction, and braking the way loose gravel really does.

Finally, two human classes turn the same maps into an endurance planner. Marathon uses elite running pace — around 21 km/h flat out — with kilometre markers and projected times over the classic 42.195 km distance, while Triathlon covers the 51.5 km Olympic format with swim, bike, and run legs drawn as separate surfaces and timed leg by leg.

Speed zones and circuit character

Once the design is complete, each segment of the track is coloured according to its calculated speed across ten bands — Full Speed, Ultra Fast, Very Fast, Fast, Medium-Fast, Medium, Medium-Slow, Slow, Very Slow, and Crawling — running from red at the flat-out end to green at the slowest. The thresholds are calibrated per class, so the same corner will show a different colour in F1 versus GT3, and the ten-band resolution makes the differences between corners visible at a glance.

The circuit also receives a character rating based on how many corners it has relative to its length. The four ratings are Ultra Technical, Technical, Balanced, and High Speed. The rating, corner count, and longest straight are all shown in the track analysis panel alongside the speed statistics.

Full analysis and FIA grading

Pressing A on a completed design opens the full analysis — a deep-dive report with a telemetry-style speed trace, three sector splits, and a corner-by-corner table listing direction, radius, apex speed, and lateral G for every turn. Braking zones are ranked by overtaking potential, a corner-balance card shows the left/right split, character ratings score the layout from 0 to 100 on pace, technicality, braking demand, flow, and power sensitivity, and a lap-time comparison runs every class over your design. The report closes with the three real-world circuits your layout most resembles, matched by length and corner density.

The FIA circuit grade card assesses your design against a deliberately simplified version of the FIA’s Appendix O requirements — length, minimum width, longest straight, run-off, and pit provision. Declare the grade you are applying for and the card shows exactly which checks pass and which licence tier the layout would earn. All figures across the analysis are model estimates for entertainment rather than engineering.

Export and sharing

You can export your circuit in three file formats from the Settings menu: GPX for sim racing software and GPS devices, KML for Google Earth and other geographic viewers, and XML for the raw waypoint and segment data — shortcuts G, K, and X jump straight to each. Pressing I opens the image export instead: your layout rendered in ten styles, from Track Card, Blueprint, and Pencil Sketch to Speed Map, Neon Nights, Vintage GP, an F1 broadcast graphic, and a to-scale satellite composite, each downloadable as a high-resolution PNG.

The share link encodes your entire design into an automatically shortened URL. Anyone who opens it sees the track exactly as you left it and can continue editing. The share panel also renders a ready-to-post track card with one-tap sharing to X, Instagram, Reddit, Facebook, and email — and the design itself lives entirely in the link.

Platform and compatibility

The app runs entirely in your browser with no installation required. It works best on desktop, where the full interface is available; mobile is fully touch-enabled — tap to place, drag to move, long-press to delete, pinch to zoom — with a bottom action bar for the essentials. No account is needed: as a guest, every design and analysis tool works and your circuit is kept in this browser, surviving a refresh but not a new device. An optional free account — sign in with an emailed code, Google, or Discord — adds the ability to save circuits and reopen them from any device.