Crash Calc

Crash Calc puts the traffic crash reconstruction formula set in your pocket. It was built by a working reconstructionist and covers the calculations you actually run at the scene, in the office and on the stand.

WHAT IS INSIDE
Eight calculator groups covering the standard reconstruction set:

Drag factors: braking, sled tests, grade and slope adjustment, superelevation, moving vehicle drag, acceleration to drag factor, degrees to percent grade
Speed and momentum: in-line momentum, angled momentum, combined speed, speed from drag and distance, speed to velocity
Kinetic energy: crush energy, energy vectors, work, energy to speed
Time, distance and velocity: the full set of solve-for combinations, with and without drag
Center of mass and radius: front, rear, roll, radius, critical speed
Airborne: level, uphill, downhill, takeoff angle
Pedestrian and motorcycle: throw distance, motorcycle slide, launch angle
Miscellaneous: swerve, tire diameter, tire speed difference, unit conversions

Every calculator shows the formula it uses, with the diagram, so you can check the work or show it to someone else.

DRAG FACTOR TEST
Measure a drag factor from an actual braking run. Deceleration is read directly from the device accelerometer across the effective braking interval, with the brake build-up and release excluded, and reported as a drag factor along with the peak value reached.

Record the surface, surface condition, tire condition and test vehicle alongside the result, so the measurement can be relied on later rather than being a bare number. Every run is saved and can be exported with the rest of your work.

The app is explicit about what the test does and does not show: it measures the deceleration that vehicle achieved on that surface at that time, which is not the same as the drag factor of the roadway. An explanation of how to use the result, and its limits, is built into the screen.

SAVED CALCULATIONS
Every result you produce is recorded automatically and grouped by session. Review them later, share a single calculation with its diagram, or export a whole session as plain text or as a PDF with the formula images included. Everything stays on your device unless you share it.

Use a saved answer to chain calculations without retyping, pulling the result of one calculator straight into a field on another.

UNITS
Metric and imperial throughout, switchable at any time.

SUBSCRIPTION
Crash Calc is a subscription app. New users get a two week free trial, then $3.99 per month or $39.99 per year. Payment is charged to your Google Play account when the trial ends. Subscriptions renew automatically unless cancelled at least 24 hours before the end of the current period. Manage or cancel at any time in Google Play under Subscriptions, or from Manage Subscription in the app menu. Cancelling stops the next renewal; access continues through the period already paid for.

Location permission is used only by the Drag Factor Test, to measure speed during a test run. Location is not stored off your device and is never shared.

Crash Calc is a calculation aid for trained investigators. Results depend on the inputs and assumptions you supply and remain your professional responsibility.