Drop D, Open G, DADGAD & Half-Step Down Guitar & Bass Tuning Frequency Chart & Tension Calculator (2026)

Retuning a 6-string guitar or 4/5-string electric bass away from E440 standard pitch changes far more than fretboard chord shapes. Every semitone you lower a wound or plain steel string reduces its mechanical pull against the truss rod according to Mersenne's Law, alters the harmonic overtone envelope seen by microphone pitch trackers, and shifts saddle intonation compensation points. Whether you are calibrating a quick 6th-string Drop D (D2 = 73.42 Hz) on our Online Guitar Tuner or locking in a sub-bass 5-string B0 (30.87 Hz) or Drop A0 (27.50 Hz) on our Online 4 & 5-String Bass Tuner, knowing the exact target Hertz values and string tension delta keeps your instrument stable and buzz-free.

Complete 6-String Guitar & 4/5-String Bass Alternate Tuning Frequency Chart (A4 = 440.00 Hz)

Under the international 12-Tone Equal Temperament (12-TET) standard anchored at A4 = 440.00 Hz, every semitone shift multiplies or divides the fundamental frequency by the twelfth root of two ($2^{1/12} \approx 1.059463$). When calibrating alternate tunings by microphone on our Online Guitar Tuner or Online Bass Tuner, checking both the scientific pitch notation (note name plus octave number) and the exact Hertz readout guarantees you never tune a string an octave too high or lock onto a second-harmonic overtone.

The Physics of String Tension: Mersenne's Law & Scale Length Compensation

Why does a guitar that plays effortlessly in E Standard suddenly buzz against the 3rd and 5th frets or drift sharp when picked hard in Drop C? The answer lies in Mersenne's Law of vibrating strings, which governs the mathematical relationship between fundamental pitch ($f$), vibrating scale length ($L$), linear mass density ($\mu$, determined by core wire plus wrap wire diameter), and mechanical string tension ($T$):

Because tension scales with the square of the frequency ($f^2$) and the square of the scale length ($L^2$), small changes in pitch or neck geometry create substantial mechanical shifts:

• 1 Semitone Down (-100 cents, e.g., E2 to Eb2): Frequency multiplies by $2^{-1/12} = 0.94387$. Squaring that factor yields $0.8909$, meaning string tension drops by 10.91%.
• 2 Semitones Down (-200 cents, e.g., E2 to D2 in Drop D): Frequency multiplies by $2^{-2/12} = 0.89090$. Squaring yields $0.7937$, meaning string tension drops by 20.63%. A .046 low E string that exerts 17.5 lbs at E2 (82.41 Hz) drops to 13.9 lbs at D2 (73.42 Hz).
• 4 Semitones Down (-400 cents, e.g., E2 to C2 in Drop C): Frequency multiplies by $2^{-4/12} = 0.79370$. Squaring yields $0.6300$, meaning tension plunges by 37.00%! Left on a standard .046 string, tension falls to nearly 11.0 lbs, causing wide elliptical string excursion, severe fret rattle, and a +35 to +50 cent sharp pitch transient every time you strike the string with a plectrum.
• Fender 25.5" vs Gibson 24.75" Scale Length: At the exact same pitch and string gauge, a 25.5" scale length requires $(25.5 / 24.75)^2 = 1.0615$, or 6.15% more tension than a 24.75" scale. Conversely, shorter-scale 24.75" guitars lose tension faster in drop tunings and typically require stepping up one full string gauge size (for example, moving from .010-.046 to .011-.052 for D Standard or Drop C).

Sub-Bass Harmonic Reconstruction: Why B0 (30.87 Hz) & E1 (41.20 Hz) Confuse Standard Tuners

Bassists who use 4-string Drop D (D1 = 36.71 Hz) or 5-string low B (B0 = 30.87 Hz) and Drop A (A0 = 27.50 Hz) frequently encounter a frustrating phenomenon on generic clip-on or browser tuners: the display rapidly flickers between octave notes or fails to register at all. Three acoustic and digital signal processing constraints explain why:

1. Acoustic Microphone Roll-Off Below 60 Hz

Small MEMS microphones built into smartphones, tablets, and laptops feature a physical diaphragm high-pass roll-off below 60 Hz to 80 Hz to prevent wind plosives from saturating the preamplifier. When you pluck a 5-string bass low B0 string at 30.87 Hz, the microphone captures far more acoustic energy at the 2nd harmonic (B1 = 61.74 Hz), the 3rd harmonic (F#2 = 92.60 Hz), and the 4th harmonic (B2 = 123.47 Hz) than at the 30.87 Hz fundamental itself.

2. FFT Window Duration vs Autocorrelation

At a 48,000 Hz audio sampling rate, a single wave cycle of B0 (30.87 Hz) spans 32.39 milliseconds (1,555 audio samples). A basic tuner using a short 1024-sample or 2048-sample buffer cannot even fit two complete periods of the waveform, making sub-cent pitch detection mathematically impossible. Our dedicated Online 4 & 5-String Bass Tuner expands the McLeod Pitch Method (MPM) autocorrelation window and tracks the common greatest divisor across the harmonic series ($f_0, 2f_0, 3f_0, 4f_0$), locking onto 30.87 Hz with ±1.5 cent stability.

3. Pickup Selection & 12th-Fret Natural Harmonic Workflow

When tuning an electric bass or baritone guitar in low drop tunings, switch to the neck pickup, roll the tone capacitor down by 30% to attenuate high-order metallic fret clank, and pluck cleanly with the fleshy pad of your thumb halfway between the neck pickup and the end of the fingerboard. If you are tuning unplugged in a noisy rehearsal space, lightly touch the string directly above the 12th fret wire to chime the 2nd harmonic (which sounds exactly one octave higher at 61.74 Hz for B0 or 73.42 Hz for D1) while locking the target string in the tuner interface.

Step-by-Step Intonation & Truss Rod Checklist When Switching Tunings

Before committing a guitar or bass to a permanent alternate tuning such as D Standard, Drop C, DADGAD, or Open G, work through this four-step calibration sequence:

1. Select Compensated String Gauges First: Use the interactive calculator above to keep individual wound string tension between 15.5 lbs and 19.5 lbs on guitar (or 36 lbs to 44 lbs on bass). If you only drop the 6th string (Drop D or Drop C), choose a hybrid "Skinny Top / Heavy Bottom" set so the treble strings remain supple for solo bends while the 6th string stays taut.
2. Tune in Multi-Pass Cycles: On floating tremolo bridges (Stratocaster 2-point tremolos or Floyd Rose locking systems) and even fixed-bridge acoustics, lowering the 6th string reduces total neck pull, causing strings 1 through 5 to go slightly sharp (+5 to +15 cents). Always perform two full tuning passes from 6th string to 1st string on the Online Guitar Tuner.
3. Check Neck Relief After 24 Hours: If total neck tension changes by more than ±8 lbs, allow the maple or mahogany neck 12 to 24 hours to settle. Hold down the 6th string at the 1st fret and the body-joint fret (15th or 17th fret) and measure clearance at the 8th fret (`0.008" to 0.010"` or `0.20mm to 0.25mm` is ideal). Tighten the truss rod clockwise in 1/8-turn increments if the neck has excessive bow, or loosen counter-clockwise if lowering tension caused a flat back-bow.
4. Recalibrate Bridge Saddle Intonation at the 12th Fret: Thicker string gauges and lower tensions shift the acoustic stiffness point at the bridge. Compare the 12th-fret natural harmonic against the fretted 12th-fret note using sustain pitch lock: if the fretted note reads sharp relative to the harmonic, move the bridge saddle away from the neck (lengthening the string); if flat, move the saddle toward the neck.