Unscrew the aerator and hold a coin against it. Quarter-size is a Standard aerator: 15/16"-27 if its threads are on the outside (male), 55/64"-27 if they’re inside (female).
What’s on the end of the spout?
Which coin is it closest to across?
Unscrew the aerator and hold coins against its end.
Start overYour aerator
A hidden (cache) aerator
A one-piece plastic aerator with male threads, screwed inside the spout. It comes out only with a key made for its size.
On the package: Key and replacement for your faucet’s cache aerator
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Start overYour aerator
Kitchen or bathroom faucet
The spout where the aerator (the little screen) screws on.
On the package: 15/16"-27 male or 55/64"-27 female aerator thread
Available on Amazon
Connect it to
Start overYour aerator
Standard aerator
Quarter-size. Threads outside (male): 15/16"-27. Threads inside (female): 55/64"-27.
On the package: Standard, 15/16 in.-27 male or 55/64 in.-27 female
Available on Amazon
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Start overYour aerator
Junior aerator
Nickel-size. Threads outside (male): 13/16"-27. Threads inside (female): 3/4"-27.
On the package: Junior, 13/16 in.-27 male or 3/4 in.-27 female
Available on Amazon
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Start overYour aerator
Tiny Junior aerator
Penny-size, with metric threads. Threads outside (male): M20x1. Threads inside (female): M19x1 in Neoperl’s sizes, M18.5x1 on Danco’s chart.
On the package: Tiny Junior, M20x1 male or M19x1 female
Available on Amazon
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Start overYour aerator
Tom Thumb aerator
Dime-size, with metric threads. Threads outside (male): M18x1. Threads inside (female): M16x1.
On the package: Tom Thumb, M18x1 male or M16x1 female
Available on Amazon
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Nickel-size is a Junior, penny-size a Tiny Junior and dime-size a Tom Thumb.
Male or female?
The name goes by the aerator, not the spout. An aerator with threads on its outside is male and screws into a spout with threads inside; one with threads inside is female and screws onto a spout with threads outside. Dual-thread aerators have both, so one part fits either spout of its size.
Faucet aerator size chart
Faucet aerator sizes
| Size | About as wide as | Male aerator (threads outside) | Female aerator (threads inside) |
|---|---|---|---|
| Standard | A quarter | 15/16"-27 | 55/64"-27 |
| Standard, metric | M24 x 1 | M22 x 1 | |
| Junior | A nickel | 13/16"-27 | 3/4"-27 |
| Tiny Junior | A penny | M20 x 1 | M19 x 1 (Danco: M18.5 x 1) |
| Tom Thumb | A dime | M18 x 1 | M16 x 1 |
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Hidden (cache) aerators
If the end of the spout shows only a plastic screen with notches and no metal ring, it’s a hidden aerator: one plastic piece with male threads that screws up inside the spout. Each thread size needs its own key to turn it. Neoperl makes them in about ten metric and inch thread sizes, from M16 x 1 to M24 x 1.5. A coin check finds the key, but it may not identify the replacement. Look up the faucet’s model, or take the old aerator to the store.
When you put a new one in, turn it gently with the key so its O-ring stays in place. Neoperl’s CACHÉ aerators go in only until they’re flush with the spout, not all the way.
Replacing an aerator
- Unscrew the old aerator counterclockwise. A service key avoids scratching the chrome; if it has been in place for a while, use adjustable pliers.
- Look up inside the spout: the rubber washer often stays behind there. Take it out before fitting the new aerator.
- Make sure the new aerator has its washer, then thread it on clockwise by hand.
- Run the water. If it drips between the spout and the aerator, take it off, seat it again, or tighten it a little more.
To keep an old housing (the metal ring) and change only the screen, take out the old insert and washer and put the new ones in the same ring.
Flow rate
Replacement aerators for kitchen and bathroom faucets in the US may flow at most 2.2 gallons per minute at 60 psi. WaterSense-labeled bathroom sink aerators use 1.5 gpm or less; WaterSense doesn’t label kitchen faucets.
Hooking up a garden hose?
Kitchen faucet to garden hose