Read the guide: How to balance a ceiling fan
How to test your ceiling fan for wobble
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Step 1: Turn the fan off and wait until the blades stop completely.
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Step 2: From a stable ladder, tape your phone to a part that doesn't turn: along the downrod just above the motor, or flat under the light kit or switch housing with the screen facing down. Use two or three wraps of strong tape, clear of the blades. Under the light kit, put a pillow on the floor below.
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Step 3: With the fan still off, tap Start (on iPhone, tap Allow). A 30-second countdown begins.
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Step 4: Climb down and switch the fan to its lowest speed right away, so it's turning steadily when the countdown ends. Stand clear, not under the fan, while it measures for 30 seconds.
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Step 5: Switch the fan off. Wait until the blades have stopped before you climb up and remove the phone. Tap Save image if you want to keep the result.
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Step 6: Fix one thing at a time, then test again with the phone in the same spot, so the results are fair to compare.
What your result means
Your result lands on one of four levels. This page uses the ceiling fan wobble scale, which is based on RMS velocity in millimeters per second (mm/s).
| Level | Range (RMS velocity) | What to do |
|---|---|---|
| Steady | Under 2.5 mm/s under 0.098 in/s | Your fan runs steadily. There is nothing to fix. |
| Slight wobble | 2.5 to 8 mm/s 0.098 to 0.315 in/s | A slight wobble like this is normal, especially on a long downrod. Tighten the blade screws if the movement bothers you. |
| Wobbly, balance it | 8 to 16 mm/s 0.315 to 0.630 in/s | Worth fixing. Tighten every screw first, then balance the blades with a clip. Test again after each change to see what helped. |
| Heavy wobble, stop and check | 16 mm/s or more 0.630 in/s or more | Switch the fan off and check how it is mounted before you run it again. If the bracket, box or downrod moves, don't use the fan until it's fixed. |
How much ceiling fan wobble is normal?
Some wobble is normal, and a ceiling fan wobble test helps you tell it apart from a real problem. A fan hangs from one point, usually on a downrod, so it sways a little as it turns. Blades are never perfectly matched, and a small difference in weight or angle pushes the fan around in a slow circle. A rule of thumb you’ll often see is that up to about 1/8 inch (3 mm) of movement is fine. Longer downrods and higher speeds make wobble easier to see.
Ceiling fan shaking matters when it gets worse over time, when you hear clicking or grinding, or when the canopy at the ceiling moves. Those point to something loose, not just a blade out of balance. A number lets you compare each fix instead of guessing by eye.
Common causes and fixes
Work through these in order. The first ones are free.
- Loose blade screws. Tighten the screws that hold each blade to its holder, and each holder to the motor. Clean the blades too, since uneven dust adds weight.
- Loose mounting. With the power off at the breaker, check the canopy screws, the mounting bracket, and the set screw and pin on the downrod. The ball at the top of the downrod must sit fully in the bracket, with its tab in the slot.
- A box not made for a fan. A ceiling fan must hang from an electrical box marked as suitable for fan support. If the box moves, call an electrician.
- Bent or warped blades. Turn the fan by hand and measure from the ceiling to the tip of each blade. If one blade sits clearly higher or lower, its holder may be bent. Replace a bent holder rather than bending it back.
- Uneven weight. If all of that checks out, balance the blades. The fan balancing tool walks you through it with a clip, one blade at a time, and the guide to balancing a ceiling fan explains the method.
When to call an electrician
Call one if the bracket or box moves when you gently push on the stopped fan, if the fan hums, grinds or smells hot, or if the reading stays at “Heavy wobble, stop and check” after you’ve tightened everything.
Reading your ceiling fan wobble test result
Uneven blades push the fan once per turn, so the Hz on your result is usually how fast the blades turn. On low, many ceiling fans turn roughly 60 to 100 times a minute, about 1 to 1.7 turns per second.
To check, pick one blade, count how many times it passes a fixed point in 10 seconds, and multiply by 6. That is the speed in RPM. If it matches the RPM on your result, the wobble follows the blades, which points to weight or blade angle. A faster peak may be the blades passing by, a rattling light kit or a loose part.
The result also estimates how far the spot under your phone moves with each turn. Blade tips move differently, so compare runs with each other rather than with the 1/8 inch rule of thumb.
Why fans get their own scale
A fan on low sways only about once a second. At that slow pace, even a tiny movement shows up as a big velocity: about 1 mm of sway already reads close to 2.7 mm/s. The machine scale used on the appliance pages would call that rough, so this page uses a scale made for ceiling fans. Its levels match roughly 1 mm, 3 mm (about 1/8 inch) and 6 mm (about 1/4 inch) of sway at the phone, back and forth along one line. Most fans wobble in a circle, which moves in both directions at once, so they reach the same levels at about two-thirds of that width: a circle roughly 0.7, 2 and 4 mm across.
What this tool can’t measure
- Blade tip movement. The reading is how fast the spot under your phone moves (velocity). It can’t tell you how far the blade tips travel.
- Higher speeds. The test is made for low speed. Check the other speeds by eye once the phone is off the fan.
- Very slow sways. The tool ignores rhythms slower than about once every two seconds.
- Wiring, motor wear or a weak box. Those need a look by hand, or an electrician.
- An official limit. There is no published standard for ceiling fan wobble. The result levels are a rule of thumb for fans on low speed. It is a good guide, not a certified measurement.
Frequently asked questions
Why not tape my phone to a fan blade?
A phone on a blade turns with the fan, so the once-per-turn wobble looks like a steady push and barely shows up. As it turns, it also tilts, which adds a false signal from gravity. On the downrod or the light kit, the phone doesn't turn, so it feels the whole fan sway.
Why is there a 30-second countdown?
It gives you time to climb down and switch the fan on after you tap Start. A fan needs a few seconds to reach a steady speed, so switch it on right away. The measurement starts when the countdown ends.
Why does my ceiling fan wobble only on high speed?
The pull from a heavy spot grows with the square of the speed. Double the speed and that pull is about four times stronger. A fan that looks steady on low can wobble clearly on high, so check every speed by eye after you finish testing.
Can a wobbling ceiling fan fall?
A wobble alone rarely brings a fan down when it hangs from a proper fan bracket. A loose bracket, or a box not made to hold a fan, is what makes a fan unsafe. If the canopy at the ceiling moves or you hear clicking, turn the fan off and check the mounting.
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