How do I read sheet music as a beginner?

Notation encodes two things — which note and how long — and reading it means learning those separately. The five lines, the clefs, note values, the time signature and the key signature, in the order that makes sense.

Difficulty: beginner
Time: 40 min
Read: 5 min

Short answer

The five lines and four spaces of the staff show pitch, higher on the page meaning higher in sound. The shape of the note head and its stem and flags show duration. The clef at the start tells you which pitches the lines represent, the time signature how the beats are grouped, and the key signature which notes are consistently sharpened or flattened.

Sheet music intimidates people because it is taught as a large body of symbols to memorise. It is better understood as two independent systems printed on top of each other: vertical position gives pitch, note shape gives duration. Learn them separately and the whole thing becomes tractable in an evening or two.

Step by step

Separate the two questions.Which note, and how long. Vertical position on the staff answers the first; the appearance of the note answers the second. Almost all beginner confusion comes from trying to absorb both at once.
Learn the staff and the clef together.Five lines and four spaces. The clef at the start fixes which pitches they represent. Treble clef is used by the right hand at a piano and by most higher instruments; bass clef by the left hand and by lower instruments. Reading a treble line as bass gives entirely the wrong notes.
Learn the note names by position, using whatever mnemonic works.In treble clef the lines from the bottom are E, G, B, D, F and the spaces spell FACE. In bass clef the lines are G, B, D, F, A and the spaces A, C, E, G. Drill them by naming notes on a page rather than by reciting the mnemonic.
Learn ledger lines as an extension of the same idea.Short lines above and below the staff continue the same alternating line-and-space pattern for notes beyond its range. Middle C sits on its own ledger line just below the treble staff and just above the bass staff, which is what connects the two.
Learn the note values as halvings.A semibreve is the longest common note, a minim is half of it, a crotchet half again, then quavers and semiquavers. A hollow head is long, a filled head shorter, a stem shorter still, and each flag or beam halves it again. It is a simple binary system.
Learn what a dot and a tie do.A dot after a note adds half its length again. A tie joins two notes of the same pitch into one longer sound. Both are extremely common and both are simple once stated.
Read the time signature as beats per bar.The top number is how many beats in a bar, the bottom number what kind of note gets one beat. Four-four means four crotchet beats. Three-four is a waltz. Six-eight groups into two lots of three. This tells you how to count, which is what makes rhythm readable.
Read the key signature as a standing instruction.Sharps or flats at the start of every line apply to those note names throughout the piece, in every octave, unless cancelled. It is a shorthand that prevents the same accidental being written hundreds of times.
Practise rhythm away from pitch.Clap or tap a line of rhythm without playing any notes. Separating the two halves is by far the fastest way to get fluent, and it is what most people never do.
Sight-read something easy every day.Fluency comes from reading a lot of easy music, not from decoding a little hard music. Five minutes a day on pieces well below your playing level improves reading faster than anything else.

Tips

Learn to read at the instrument, not away from it. The connection you want is between the symbol and the physical action, and building it through note names as an intermediate step is slower.
Write the note names in above a passage if you are stuck, then rub them out and read it again. It is a scaffold, and the trap is leaving them in permanently.
A metronome makes rhythm concrete. Reading rhythm without a beat to attach it to is guesswork.

Common mistakes

Trying to learn every symbol before playing anything — Notation has a very long tail of markings, most of which are rare. The staff, the clef, note values, the time signature and the key signature cover the overwhelming majority of what appears on a page.
Reading pitch and ignoring rhythm — Rhythm is what makes music recognisable. A passage with correct notes and wrong rhythm is unrecognisable; correct rhythm with a wrong note is barely noticed.
Only ever practising difficult pieces — Sight-reading is a fluency skill and fluency is built on volume. Reading many easy pieces builds it; grinding through one hard one does not.
Relying on note-name mnemonics permanently — They are training wheels. Recognising the position directly is much faster, and it comes from drilling positions rather than reciting the phrase every time.

If it doesn't work

The notes come out wrong across the whole piece

Cause: Reading the wrong clef, or ignoring the key signature — Fix: Check the clef at the start of the line and the sharps or flats in the key signature. Both apply for the whole piece.

You can read pitch but not rhythm

Cause: Rhythm never practised separately — Fix: Clap rhythms with a metronome, with no instrument involved. Rhythm is a distinct skill and it responds quickly to isolated practice.

Reading is much slower than playing by ear

Cause: Normal early on, and it persists if reading is avoided — Fix: Five minutes of easy sight-reading daily. The gap closes with volume of reading, not with effort on hard material.

You lose your place on the page

Cause: Looking down at your hands — Fix: Practise keeping your eyes on the page and feeling for the instrument. It feels impossible and becomes automatic surprisingly fast.

An accidental appears mid-bar and confuses you

Cause: An accidental applies for the rest of that bar only — Fix: A sharp, flat or natural written in the music affects that note for the remainder of that bar, then the key signature resumes.

Questions people ask

Do I need to read music to play an instrument?

No, and a great many excellent musicians do not. It becomes valuable when you want to play with others from parts, learn repertoire that is not tabbed, or understand what you are playing. It is a tool, not a requirement.

How long does it take to learn?

The system itself takes an evening or two to understand. Fluency — reading at speed without decoding — takes months of regular easy sight-reading, and it never entirely stops improving.

Is it different for each instrument?

The system is the same. What differs is which clef you read, whether you read one line or two, and instrument-specific markings such as bowing, breathing or fingering. Learning it once transfers substantially.