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Kinetic energy and momentum calculator

Calculate kinetic energy and momentum from mass and velocity, plus work and power.

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Kinetic energy and momentum calculator
Paste a mass and a velocity, separated by a semicolon, and this tool returns the kinetic energy (KE = ½mv²) and momentum (p = mv) instantly. It accepts a whole list of bodies, one per line — useful for comparing moving objects, checking a physics assignment, or running quick "what if" numbers for a design — and reports a running total across every line you paste in.
Choose the units that fit your problem: mass in kilograms, grams or pounds; velocity in meters per second, kilometers per hour or miles per hour; energy in joules, kilojoules, kilowatt-hours or kilocalories. Add a force and a distance to a line (mass;velocity;force;distance) to also see the work done (W = F × d) and the instantaneous power (P = F × v). If a line is missing its mass or velocity but gives a force and a distance, the tool recovers it with the work–energy theorem, assuming the body started at rest. Turn on "Two-body momentum conservation" with exactly two lines to see the combined velocity after a perfectly inelastic collision, or set a height to add the potential energy (PE = mgh) at that height.
Lines can use a comma or a period as the decimal separator, and Windows (CRLF) or Unix (LF) line endings are handled the same way. A line that can't be parsed, or that doesn't give enough to solve, is reported inline with the reason rather than stopping the whole calculation — every other line still gets an answer. The decimal places option sets how many digits results are rounded to.
Everything runs locally in your browser using plain arithmetic — no numbers are ever uploaded anywhere. Copy the result, download it as a .txt file, or send it back into the input to adjust a value and recalculate.
FAQ
What input format does it expect?
One body per line, as mass;velocity — for example 2;5. Add a force and a distance as mass;velocity;force;distance to also get work and power for that line.
Can it work out a missing mass or velocity?
Yes, when a line gives a force and a distance alongside the one value it does have. The tool applies the work–energy theorem (force × distance = kinetic energy gained), assuming the body starts from rest, to solve for the missing quantity.
What does "Two-body momentum conservation" show?
With exactly two lines and the option turned on, it reports the combined velocity the two bodies would share after a perfectly inelastic collision, using conservation of momentum.
Why did a line come back as an error instead of a number?
Either it could not be parsed as numbers (check the semicolons and that only digits, a decimal separator and a minus sign appear), or it does not give enough information — mass and velocity, or one of them plus a force and a distance, are required.
Is my data uploaded anywhere?
No. Every calculation runs in your browser using plain JavaScript arithmetic — nothing you type is sent to a server.