NMR ppm to Hz Converter

Convert NMR chemical shifts (δ) in ppm to frequency in Hz (or vice versa) using the spectrometer reference frequency. For students, researchers, and lab technicians. All calculations run entirely offline in your browser.

Note: Educational only. Follow your lab SOPs and SDS for instrument operation and calibration.

Converter

Spectrometer Frequency (MHz)

Enter the Larmor frequency of your nucleus (e.g., 400 MHz for ¹H).

Chemical Shift δ (ppm)

Parts per million relative to reference.

Frequency Offset (Hz)

Absolute frequency difference from reference.

Result

Frequency offset: 1000 Hz

Equation: Δν (Hz) = δ (ppm) × ν₀ (MHz)

Reference frequency: 400.0 MHz

Understanding NMR ppm to Hz Conversion

NMR chemical shifts are reported in ppm (parts per million), which is a dimensionless, field-independent unit. However, for instrument setup, pulse calibration, and spectral analysis, you often need the absolute frequency offset in Hz.

Why this matters: Direct frequency values are needed for setting spectral widths, transmitter offsets, and understanding coupling constants in Hz.

Step-by-Step Usage

Enter your spectrometer frequency for the nucleus (e.g., 500 MHz for ¹H).
Enter a chemical shift in ppm. The Hz offset will auto‑calculate.
To convert Hz to ppm, click "Swap Input/Output", enter the Hz value, and ppm will be calculated.
Use "Copy Result" to paste into your lab notebook.

Realistic Examples

ν₀ (MHz)	δ (ppm)	Δν (Hz)	Note
300	7.26	2178	CHCl₃ in CDCl₃ (¹H)
600	0.0	0	Reference (TMS)
125	77.0	9625	CDCl₃ central peak (¹³C)

Common Mistakes

Using the wrong spectrometer frequency (e.g., 400 MHz for ¹³C when it's for ¹H).
Confusing Hz with ppm when reporting coupling constants (always Hz).
Forgetting that ppm is field‑independent, but Hz changes with field strength.

Common NMR Frequency Lookup

Select a nucleus and common field strength to see typical frequencies. The ppm input above will update with the selected frequency.

Nucleus

Magnetic Field Strength

Nucleus	γ (10⁷ rad·T⁻¹·s⁻¹)	Field (T)	ν₀ (MHz)	Action

Gyromagnetic ratios (γ) from IUPAC recommendations. Frequencies are calculated as ν₀ = (γ · B₀) / (2π).

Frequently Asked Questions

What are the accuracy limits of this converter?

The calculation is mathematically exact. Accuracy depends on your input values. Spectrometer frequencies are nominal; actual values may differ by ±0.1% due to calibration and temperature. Always calibrate with a known reference.

Why does the same ppm value give different Hz on different instruments?

Because ppm is field‑independent (δ = Δν/ν₀), but Hz scales linearly with the spectrometer frequency (ν₀). A 1 ppm shift is 400 Hz at 400 MHz, but 600 Hz at 600 MHz.

How do I convert coupling constants (J) from ppm to Hz?

Coupling constants are always reported in Hz and do not depend on field strength. Never convert J‑couplings to ppm; they are constant in Hz across different spectrometers.

What if my nucleus has a different reference frequency?

Enter the actual Larmor frequency for your nucleus at your field. Use the lookup table above for common nuclei, or consult your instrument’s console or manual.

Formulas & Assumptions

Core equation: Δν (Hz) = δ (ppm) × ν₀ (MHz)
Reverse equation: δ (ppm) = Δν (Hz) ÷ ν₀ (MHz)
Assumptions: Linear relationship, negligible second‑order effects, and referenced to δ = 0 ppm at Δν = 0 Hz.
Rounding policy: Results displayed to 4 decimal places for ppm, 2 for Hz. Internal calculations use full precision.
Constants: Uses exact arithmetic; no physical constants beyond your input ν₀.

Legal Disclaimer

For informational and educational purposes only. Estimates depend on your inputs and simplifying assumptions. This tool does not replace professional judgment, lab SOPs, or safety procedures. Always follow SDS guidance and institutional policies.

Sources & References

Common chemistry constants: R, Nₐ, F

Standard unit conversions and lab measurement best practices

IUPAC recommendations for NMR spectroscopy

Laboratory safety basics and SDS principles

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NMR ppm to Hz Converter

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