Key Signature Calculation (Music Theory Lesson)

30 different key signatures exist (15 for major scales and 15 for minor scales). Most theory students are expected to memorize all 30.

Fortunately, using the key signature calculation method, one only has to memorize seven.

In the calculation method, each key signature is assigned a numeric value based on the number and type of accidentals. Sharps are positive; flats are negative.

The key of C Major has no accidentals; therefore, its numeric value is 0.

The key of D Major has two sharps; thus, its numeric value is 2.

The key of E Major has four sharps - a numeric value of 4.

The key of F Major has one flat; therefore, its numeric value is -1. (Remember: flats are assigned negative numbers)

The key of G Major has one sharp. Its numeric value is 1.

The key of A Major has three sharps - a numeric value of 3.

Finally, the key of B Major has five sharps - giving it a numeric value of 5.

These seven values must be memorized before we can proceed.

Next, let's compare Cb, C, and C# Major.

If we start at C Major and subtract 7, we end up at Cb Major.

If we start at C Major and add 7, we end up at C# Major.

These two numeric relationships can help us calculate keys that we do not know.

Let's figure out Eb Major. First, start with E Major, which has a numeric value of 4.

To convert to Eb Major, subtract 7.

The result is -3; thus, Eb Major has 3 flats.

Let's try F# Major. Start with F Major, which is -1.

To convert to F# Major, add 7.

The result is 6; thus, F# Major has 6 sharps.

Next, we will examine minor scales. Compare C Major and C Minor.

To convert a major scale into its parallel minor, simply subtract 3.

Let's calculate D Minor. We will start with D Major, which is 2.

Next, simply subtract 3.

The result is -1. Therefore, D Minor has one 1 flat.

Next, let's try F Minor. We will start with F Major, which is -1.

Next, subtract 3.

The result is -4. Thus, F Minor has 4 flats.

Some key signatures require two conversions. For example, let's calculate G# Minor.

Start with G Major, which has a numeric value of 1.

Next, add 7 to get to G# Major.

Finally, subtract 3 to convert to G# Minor.

The result is 5. G# Minor therefore has 5 sharps.

Using the calculation method, it is possible to calculate key signatures which have more than seven accidentals.

- Lesson 1Staffs, Clefs and Ledger Lines
- Lesson 2Note Duration
- Lesson 3Measures and Time Signature
- Lesson 4Rest Duration
- Lesson 5Dots and Ties
- Lesson 6Simple and Compound Meter
- Lesson 7Odd Meter
- Lesson 8Steps and Accidentals
- Lesson 9The Major Scale
- Lesson 10The Minor Scales
- Lesson 11Introduction to Major Chords
- Lesson 12An Introduction to Minor Chords
- Lesson 13Scale Degrees
- Lesson 14Key Signatures
- Lesson 15An Introduction to Major Scales
- Lesson 16Key Signature Calculation
- Lesson 17Generic Intervals
- Lesson 18Specific Intervals
- Lesson 19Introduction Staff and Clefs
- Lesson 20Writing Intervals
- Lesson 21Interval Inversion
- Lesson 22Introduction to Chords
- Lesson 23Triad Inversion
- Lesson 24Diatonic Triads
- Lesson 25Roman Numeral Analysis
- Lesson 26Voicing Chords
- Lesson 27Analysis #1
- Lesson 28Seventh Chords
- Lesson 29Diatonic Seventh Chords
- Lesson 30Seventh Chord Inversion
- Lesson 31Composing with Minor Scales
- Lesson 32Nonharmonic Tones
- Lesson 33Phrases and Cadences
- Lesson 34Circle Progressions
- Lesson 35Common Chord Progressions
- Lesson 36Triads in First Inversion
- Lesson 37Triads in Second Inversion
- Lesson 38Analysis #2
- Lesson 39Building Neapolitan Chords
- Lesson 40Using Neapolitan Chords
- Lesson 41Analysis #3
- Lesson 42Instrument Ranges
- Lesson 43Introduction to the pentatonic scale
- Lesson 44Introduction to Modes
- Lesson 45Degrees of the scale
- Lesson 46Introduction to Triads
- Lesson 47Music Glossary
- Music TrainingInterval Trainer
- Music TrainingNote Trainer
- Music TrainingKey Trainer
- Music TrainingTriad Trainer
- Music TrainingKeyboard Trainer
- Music TrainingGuitar Trainer
- Music TrainingBrass Trainer
- Music TrainingInterval Ear Trainer
- Music TrainingScale Ear Trainer
- Music TrainingChord Ear Trainer

All music theory articles are copyright Ricci Adams, reproduced by kind permission. Except where otherwise noted, these theory lessons are licensed under a Creative Commons License.

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