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Engine Horsepower Calculator – (Using Acceleration Times)

Car Instrument Cluster During Acceleration

Calculate your engine's power with nothing but a stopwatch and some simple specs.

This engine horsepower calculator will calculate the horsepower of your engine by using the car’s acceleration times.

It will give you the power in KW, BHP & PS @ the flywheel.

It will also give you the torque in lbs/ft and NM @ the flywheel

Things We Need

  • Straight piece of road with constant gradient
  • Video camera to film speedometer (or the OBD speed for more accurate reading)
  • Video editing software (or video player where we can see individual frames)
  • The engine horsepower calculator (below)
  • Vehicles specs, specifically
    Weight of vehicle
    Gear ratio
    Final drive
    Tyre size

You can find the car specs here

The Method – How to use this engine horsepower calculator

  • On the straight piece of road, in the gear of your choice, film the speedo as you accelerate from your chosen start speed to finish speed and as you coast (in neutral, foot off clutch) back down to your start speed (Gear, and start and end speed is entirely up to you).
  • Choose the size of the recorded speed segment (5km/h is a good starting point) and using the video editing software, note down the time it took the car to accelerate over each segment and note down the time it took to decelerate (coast down) through each interval
  • Enter the specs of the vehicle below and for each speed segment, enter the start and finish speed, the acceleration time and the coast down time. The engine horsepower calculator will automatically output the RPM, horsepower & torque of the engine for each interval.

Increasing Accuracy

  • For maximum accuracy the road should have a consistent gradient for the whole run
  • Using a digital speedometer or filming the speed from the OBD output will eliminate the parallax error of the speedo needle.
  • Multiple runs to get an average
  • Smaller speed segments

Quick and easy and no need to do runs in both directions!

Any questions? Leave a comment below!

Real World Example

We have tested this calculator on a Ford Focus MK1 1.6. Using the data from

The engine horsepower calculator calculated the peak flywheel power at around 95BHP and peak torque of 145NM.

We have previously dynoed this car and we got a horsepower figure of 100BHP and torque of 140NM.

In short, we think this calculator can be very accurate

Create a Dyno Graph!

You can also make a dyno graph using this calculator.

Plot the data into excel (with RPM along X-axis and horspower on Y-axis) to get your dynograph.

Want to calculate other things? Check out our other calculators here

This page was last modified Feb 26, 2022 @ 2:54 am

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