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Doppler Effect Calculator

Work out the perceived frequency for a moving source or observer, classically f' = f(v ± v_o)/(v ∓ v_s) with real sound speeds, or relativistically for light — supersonic sources flagged.

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Open Doppler Effect Calculator and you get an answer straight away, with no account to create. You will find it under Physics, with Angular Velocity Calculator and Coulomb's Law Calculator for the neighbouring cases.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Doppler Effect Calculator do?

Work out the perceived frequency for a moving source or observer, classically f' = f(v ± v_o)/(v ∓ v_s) with real sound speeds, or relativistically for light — supersonic sources flagged.

When would I actually use this?

Checking a homework answer, sizing something before building it, and getting an order of magnitude before committing to a design — a torque on a bolt, the force a spring returns, the frequency a circuit resonates at, how long light takes to arrive.

What is the most common mistake?

Feeding in a value in the wrong unit. Physics formulas assume SI throughout, so grams instead of kilograms or centimetres instead of metres shifts the answer by powers of ten without any warning.

Is there a tool for the next step?

Coulomb's Law Calculator is the closest one after this: Solve F = kq₁q₂/εᵣr² for the force, either charge or the distance, in any of 18 dielectric media, with charges in C, µC, nC or elementary charges, plus the potential energy and the field at q₂.

What else is worth having open alongside it?

de Broglie Wavelength Calculator and Decibel (dB) Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Constants are the CODATA values and the formulas are the textbook ones. Most assume an idealised case — no air resistance, no friction, a point mass — and the tool says so where the simplification matters.

Further reading

All guides →
ExplainerHow the Doppler Effect Works: The Formula, the Sign Convention, and Why Moving the Source Is Not the Same as Moving the ListenerFor sound, f' = f(v + v_o)/(v − v_s) — and getting the signs backwards is the classic error. Here is the convention spelled out, a 440 Hz source computed at four speeds, and why light needs a different equation entirely.ExplainerA Stiletto Heel Presses Forty-Eight Times Harder Than an ElephantA 60 kg person on one square centimetre of heel exerts 5.89 MPa. A five-tonne elephant on four feet of 0.1 m² each exerts 123 kPa. Same physics, opposite areas.ExplainerSound Travels Faster in Steel Because of Stiffness, Not Density343 m/s in air at 20 °C, 1,481 in water, 5,960 in steel and 12,000 in diamond. Steel is 6,500 times denser than air and carries sound only 17 times faster — density slows sound down.ExplainerFriction Does Not Care How Big the Contact Patch IsA coefficient of 0.3 against a normal force of 100 N gives 30 N of friction, and the area never enters the formula. What does enter it, and is usually got wrong, is the normal force.ExplainerA Party Balloon Lifts Fourteen Grams, Not Its Own VolumeA 28 cm latex balloon nets 14 g of lift, so a kilogram takes 72 of them. At 2,000 metres the same balloon lifts 21 % less and you need 91.ExplainerA Kitchen Scale and a Jug Tell You If That Tap Is Really BrassWeigh it, sink it in water, divide. 340 g displacing 40 cm³ is 8.5 g/cm³ and brass; 272 g in the same 40 cm³ is 6.8 and a zinc casting wearing brass plate.