Measure your smash speed with just a phone

To measure badminton smash speed with a phone, film the smash side-on in slow motion (120 or 240 fps), count how many frames the shuttle takes to cover a known distance just after contact, and divide: speed = distance × frame rate ÷ frames. The other two options are a sports radar gun or an app that tracks the shuttle automatically.

All three can work. All three can also give you a confident, wrong number. The difference is in a few details: measuring the speed right off the racket instead of an average, filming at the right angle, and knowing how precise your method really is. This guide covers each method step by step, with a calculator and a demo that shows exactly how a bad camera angle fools you.

Three ways to measure smash speed

No consumer method matches the lab setups used for world records (the 2023 Guinness records were reportedly measured with a camera shooting 40,000 frames per second). Aim for consistent, honest numbers you can compare with your own past results.

Method 1: count frames in a slow-motion video

This is the classic badminton smash speed test, and it costs nothing. Most recent phones film slow motion at 120 or 240 frames per second, which is enough if you are careful.

1. Set the phone side-on. Put the phone on a tripod or prop beside the court, level with the smash, so it looks across the flight path at a right angle. Stand it several meters back so the whole first two meters of flight are in frame.
2. Put a known distance in the same plane. Use a court marking or a measured stick lying along the line the shuttle will fly, at the same distance from the camera as the smash. On a badminton court, the net to the short service line is 1.98 m and the back boundary line to the doubles long service line is 0.76 m.
3. Film in slow motion. Record at 120 or 240 frames per second in bright light, so the shuttle is sharp rather than a streak. Check the camera's real capture frame rate in its settings.
4. Find the contact frame. Step through the clip frame by frame and mark the first frame where the shuttle has clearly left the strings. Call this frame A.
5. Step forward a few frames. Move forward 2 to 6 frames, enough for the shuttle to travel about 0.5 to 1.5 m. Call this frame B and note how many frames apart A and B are.
6. Measure the distance travelled. Using your reference length for scale, measure how far the shuttle's cork moved between frame A and frame B.
7. Calculate and correct. Speed = distance × frame rate ÷ frames. Because the shuttle slows from the moment it leaves the strings, correct the average upward for drag, or keep the stretch short. Repeat for five smashes and report your best and your typical speed.

Plug your numbers into the mini calculator. It shows the raw average and a drag-corrected estimate of the speed off the racket.

Why the frame rate matters so much

A 200 km/h (124 mph) smash travels about 1.85 m between frames at 30 fps, 0.46 m at 120 fps and 0.23 m at 240 fps. At 30 fps the shuttle is a blur that jumps most of the way to the net between frames, so you can neither find the contact moment nor place the shuttle precisely. At 240 fps you get several sharp positions in the first meter. Higher is better, as long as there is enough light to keep the shuttle from smearing.

Why the stretch should be short

A shuttle slows down from the instant it leaves the strings: research on elite smashes (Collet, 2026) found its speed halves about every 3.35 m. So the longer the stretch you time, the more your average under-reads the release speed. Using that model, the average over the first 1 m is about 90% of the release speed; over 3 m, only about 72%. Keep the stretch to roughly 0.5 to 1.5 m, or use the drag correction above.

For the full version with more options, use the smash speed calculator.

Method 2: a radar gun

Sports radars measure speed directly using the Doppler effect, and researchers use them: Phomsoupha and Laffaye (2014) measured 77 players with a radar sampling at 250 Hz, placed 3 m behind the player and about 2.5 m high, in line with the target. That placement is the key. A radar only reads the part of the motion heading straight along its beam, so a radar off to the side reads low. The error grows with the angle: at 20° off the line the reading is about 6% low, at 30° about 13% low.

• Mount it behind the hitter, in line with the smash direction, at roughly head height or above.
• Smash at a fixed target so the line stays the same every time.
• Record many smashes and keep the best few; aim errors only ever make the number lower.

Method 3: an app that tracks the shuttle

A badminton smash speed app does the frame counting for you, for every smash, during real rallies rather than a feeding drill. That matters, because your match smashes are the ones that win points, and they are usually slower than your best fed smash.

Single-camera tracking has limits too: it has to estimate depth from one viewpoint, which is why setup matters. See where to put your phone and how to film badminton for the best angle and settings.

Common mistakes (and how big they are)

Measuring average speed instead of initial speed

Timing the shuttle from contact to landing gives you an average over 8 to 12 m, which can be less than half the speed off the racket. Records and studies quote initial speed. Compare like with like.

Filming at an angle, or with the wrong scale

This is the big one, and it is invisible in the video. If the flight is angled towards or away from the camera, it looks shorter, so the speed reads low. If the shuttle is nearer the camera than the reference you measured with, it looks bigger, so the speed reads high. Try it:

With the camera 7 m from the reference line, a 20° angle under-reads a 300 km/h smash by about 5%, and a 30° angle by about 12%. A shuttle just 1 m nearer than the reference over-reads by about 17%. Worse, the two errors can cancel or stack without you knowing: a 30° angle and a 1 m offset can land you within 3% by pure luck. Side-on filming and a reference in the same plane as the smash are the only reliable fix.

Trusting the slow-mo playback speed

Slow-motion clips play back at normal speed, so time on the scrubber is not real time. Count frames and use the capture frame rate from the camera settings, not seconds on the playback bar.

One smash, one number

Single readings bounce around. Measure five or more and report your best and your typical speed. That is also how you should compare with the ranges in average smash speed by level.

Once you have a number

Track it over weeks, measured the same way. If it isn't moving, the fix is almost always technique: read how to smash harder for the kinetic chain, contact point and drills.