A standard ukulele is tuned G-C-E-A, from the string nearest your face to the one nearest the floor. The G is tuned high, so the C string is the lowest note on the instrument. Set a tuner to chromatic or ukulele mode, bring each string up to its note, then go round all four again. If a new ukulele keeps sliding flat after that, it's normal, and the second half of this guide explains why.
The four notes, and the G that sits high
On a standard ukulele, string 4, nearest your chin, is the G. Then come C and E, with string 1, the A, nearest the floor. The G string is tuned high, above the C string beside it, and that's what surprises guitar players.
Play from string 4 to string 1 and the pitch drops from G to C, then climbs through E to A. This is called re-entrant tuning. The C string sits at middle C, and it's the lowest note a standard ukulele can play. Soprano, concert and tenor ukuleles all use this tuning, and the baritone is the exception, covered at the end.
To hear the four notes, sing "My Dog Has Fleas" as you pluck the open strings from G to A, one word per string. The tune matches the four pitches (the first letters of the words don't spell G-C-E-A), and it gives you the sound to listen for.
Using a tuner, one step at a time
You don't need anything expensive. A clip-on tuner reads the vibration through the headstock, so it works in a noisy room, while a phone app or online tuner listens through the microphone and does best somewhere quiet.
Set the tuner to chromatic or ukulele mode. In guitar-only mode it listens for guitar strings and can misread your C.
Pluck string 4, the G, and let it ring.
Read the display. Left of centre means the string is flat, or too low, and right of centre means it's sharp, or too high.
Tighten the peg to raise the pitch and loosen it to lower it. Turn slowly while the string rings and watch which way the reading moves, because the direction isn't the same on every ukulele. Small turns also keep you from over-tightening and breaking a string.
If you go past the note, loosen the string below it and bring it back up. Finishing on an upward turn takes the slack out of the string at the peg, so it holds.
Do the same for the C, E and A strings.
Go round all four again. Raising one string pulls on the neck and can nudge the others.
Then listen as well as look. A tuner shows "G" for a high G and a low G alike, so the letter on the screen doesn't prove the octave. On a standard ukulele the G should sound higher than the C. If every string reads correctly but your chords sound wrong, one string is probably an octave off, usually the G.
Tuning without a tuner
You can tune the ukulele to itself once one string is right. Start by tuning the A string to a piano, a tuning fork or another instrument.
Press the E string at the 5th fret. That note is an A, so tune the E string until it matches the open A string.
Press the C string at the 4th fret. That note is an E, so tune the C string until it matches the open E string.
Press the G string at the 2nd fret. That note is an A, so tune the G string until it matches the open A string.
This puts the ukulele in tune with itself, and only with itself. If your first string was off, everything follows it, and you'll clash with anyone you play with. Check your work with two chords. Strum a C chord (fret numbers 0003) and a G chord (0232), and if one string sounds sour in both, retune that string.
Why your ukulele won't stay in tune
A ukulele that holds its tuning has settled strings and pegs that are tight enough. When yours drifts, the cause is usually new strings that are still settling, a peg that slips, a string catching in the nut, a change of room, or old strings. Start with the strings, because cheap and expensive ukuleles alike go through that settling period.
New strings that keep going flat
A new or freshly restrung ukulele goes flat again soon after you tune it, sometimes within minutes, and that's normal. Nylon and fluorocarbon strings keep stretching after they're first brought to pitch, and the strings on a new ukulele have usually never been at pitch at all. They can also slip a little at the bridge knot until it pulls tight.
How long it lasts depends on the string material and how much you play. Expect anything from a day or two to a couple of weeks, with fluorocarbon at the quicker end and nylon at the slower one.
Advice differs on whether to stretch new strings by hand. If you do, keep it gentle: pull each string a little way from the fingerboard a few times, retune, and repeat until it holds, with your palm on the bridge so you pull the string and not the bridge. Or keep playing and retuning until the strings settle. Either way, retune often for the first few days.
A peg that slips back
Friction pegs hold by friction alone, set by the screw at the end of each peg. If a string keeps slipping flat, tighten that screw a quarter turn at a time until the peg holds. Go too far and the peg won't turn.
Geared pegs are different. Their screw only holds the button on, so a geared peg that turns backward under string tension is broken, and that one is a job for a repair shop. A string with too few winds around the post, or a loose bridge knot, can slip the same way, and restringing it neatly sorts it out.
A string that jumps with a little ping
If a string sticks while you tune and then jumps in pitch with a small ping, it's catching in the nut, the slotted piece at the top of the neck. This is less common than settling strings or a slipping peg. A little pencil graphite in the slot helps if the string is actually binding. If the slot is too narrow, have a repair shop widen it rather than filing it yourself.
Drift when the room changes
Moving from a cold room to a warm one, or playing under stage lights, shifts the tuning, so give the ukulele a few minutes before you tune it. Fluorocarbon strings are generally reported as the most stable in changing conditions, and nylon is more sensitive. Solid-wood ukuleles are also sensitive to swings in temperature and humidity, so avoid sudden changes for the instrument's sake.
Old strings that won't hold anymore
Strings wear out. The signs are a dull sound, tuning that won't hold anymore, and notes that sound out of tune on some chords but not others. There's no set schedule for replacing them, because it depends on how much and how hard you play. A wound low-G string often wears out first, and you can replace it on its own.
How often to retune
Check the tuning every time you pick the ukulele up. With a new set of strings, you'll retune often, sometimes more than once in a practice session, while they settle. Once they have, a light touch-up before you play is usually enough. If you find yourself retuning more and more again later on, the strings are getting old, and a fresh set is the fix.
Tuning in a lesson
A free tuner and the steps in this guide are enough to tune on your own, and several of the fixes in this guide are things you can do at home. Tuning is part of what I cover in ukulele lessons.
I was Artistic Director of the Victoria Ukulele Festival in 2017, and I teach ukulele live online, one-to-one on Zoom, to students anywhere in Canada and in the US. I also teach in person in Victoria, BC, where the beginner group class covers tuning the instrument too. If you'd like some help getting started, have a look at my online ukulele lessons, or tell me what kind of ukulele you're tuning.
Tuning questions from new ukulele owners
Can I use a guitar tuner or guitar tuning app on a ukulele?
A guitar tuner or tuning app works on a ukulele if it has a chromatic or ukulele mode. In guitar-only mode, a tuner looks for the six guitar strings and may misread your C string. The display shows only the note name, so listen as well: on a standard ukulele, the G string should sound higher than the C.
Does a new ukulele come in tune?
Most new ukuleles don't arrive in tune, and one that arrives close won't stay there at first. Its strings have usually never been brought up to pitch, so they keep stretching and can slip at the bridge knot. Expect to retune often until they settle, which can take from a day or two to a couple of weeks.
Should I loosen the strings when I'm not playing?
For everyday breaks, one ukulele maker's care guide says there's no need to loosen the strings and advises keeping the ukulele at standard tuning, which helps the strings settle. For storage of a few months or longer, the same guide advises loosening the strings to ease the tension on the neck.
What changes with a low-G string, and does it add an octave?
A low-G string is tuned an octave below the usual high G, so the strings run in order from low to high. The ukulele doesn't gain an octave of range, though. Its lowest note moves from middle C down to the low G, five semitones lower (a perfect fourth). It needs a string made for low G, and chord shapes and names stay the same.
How do I tune a baritone ukulele?
A baritone ukulele is tuned D-G-B-E, the same notes as the four highest strings of a guitar, with no high string. Use a tuner in chromatic mode. Without one, get the E string right first, then match the B string at the 5th fret to the open E, the G at the 4th fret to the open B, and the D at the 5th fret to the open G.
Why does it sound out of tune when the tuner says every string is right?
When a ukulele sounds out of tune but the tuner shows every string right, usually one string is an octave off, or the problem is intonation. On a standard ukulele the G should sound higher than the C. If the open strings are right but chords higher up the neck sound off, that's intonation, which depends on the bridge and nut. A setup at a repair shop fixes it, and retuning won't.