Frequency Range Calculator: Find the Span in Hz

A frequency range calculator finds the span between a lower and an upper frequency: enter both values in hertz, and it returns the range width and midpoint. It also converts the endpoints and results to kilohertz or megahertz when useful.

Formula

The frequency range, or bandwidth as a simple difference, is the upper frequency minus the lower frequency:

Range width = f_high − f_low

• f_low is the lower endpoint, in hertz (Hz).
• f_high is the upper endpoint, in hertz (Hz).
• Range width is the difference between the endpoints, also in Hz.

The calculator also gives the arithmetic midpoint, (f_low + f_high) / 2, and the upper-to-lower ratio, f_high / f_low. The midpoint is in Hz; the ratio has no unit. A valid range requires the upper endpoint to be at least as large as the lower endpoint. A ratio requires a nonzero lower endpoint.

Worked Example

Using the calculator’s default values, the lower frequency is 100 Hz and the upper frequency is 1,000 Hz.

1. Range width = 1,000 − 100 = 900 Hz.
2. Arithmetic midpoint = (100 + 1,000) / 2 = 550 Hz.
3. Upper-to-lower ratio = 1,000 / 100 = 10.

The calculator rounds the width and midpoint to two decimal places and the ratio to three, so it displays 900.00 Hz, 550.00 Hz, and 10.000.

What a Frequency Range Means

Frequency measures how many cycles of a repeating event occur per second. One hertz is one cycle per second. A frequency range describes the interval from one frequency to another; it does not, by itself, say how strong a signal is, how much information it carries, or whether a particular device can receive it.

For example, a system that operates from 100 Hz to 1,000 Hz covers a width of 900 Hz. The endpoints and width answer different questions: “100–1,000 Hz” identifies the covered interval, while “900 Hz bandwidth” gives its numerical span. Always state the endpoints when the location of the interval matters, because many different frequency ranges can have the same width.

Frequency ranges appear in audio, radio, electronics, vibration measurements, signal processing, and wave descriptions. The relevant meaning can depend on context. In communications, for instance, a stated channel allocation is not necessarily the same as the signal’s occupied bandwidth, which depends on the signal and the measurement convention.

How to Enter Frequencies and Convert Units

Enter both values in the same unit. This calculator accepts hertz and allows values up to 1,000,000,000,000 Hz. It rejects a negative frequency and reports an invalid range if the upper endpoint is below the lower one. The ratio is undefined when the lower endpoint is zero.

Common frequency units are related by powers of 1,000:

• 1 kHz = 1,000 Hz.
• 1 MHz = 1,000,000 Hz.
• 1 GHz = 1,000,000,000 Hz.
• 1 THz = 1,000,000,000,000 Hz.

Convert before subtracting. For a range from 2.4 GHz to 2.5 GHz, enter 2,400,000,000 Hz and 2,500,000,000 Hz. The difference is 100,000,000 Hz, or 100 MHz. Subtracting the displayed numbers 2.5 − 2.4 gives 0.1, but that answer is in GHz—not Hz. The arithmetic is valid only when the units are consistent.

Reading the Results and Choosing the Right Measure

The first result is the range width. It is a simple absolute difference, useful when you need to know how many hertz separate the endpoints. The midpoint is the center by ordinary arithmetic, not necessarily the center used in every technical convention. The ratio compares the upper endpoint with the lower one and helps describe how broad the interval is proportionally.

Some applications describe ranges on a logarithmic scale, where equal ratios rather than equal differences represent equal steps. For example, the arithmetic midpoint of 100 Hz and 1,000 Hz is 550 Hz. The geometric midpoint is √(100 × 1,000), about 316.23 Hz. Neither is universally “correct”: use the arithmetic midpoint for a linear scale and the geometric midpoint where a logarithmic or octave-based interpretation is intended.

For the same reason, the calculator’s ratio is not a decibel value. A frequency ratio can be converted to an octave span using log₂(f_high / f_low) when both endpoints are positive. A difference in frequency, a frequency ratio, and a signal level in decibels are distinct quantities.

Common Mistakes and Limits

• Mixing units: Convert both endpoints to Hz, or to the same other unit, before subtracting.
• Reversing endpoints: Put the smaller frequency in the lower-frequency field. A negative difference is not a valid range width.
• Confusing range with center frequency: The width alone does not identify where a band lies.
• Assuming the range describes performance: A calculated interval does not establish a device’s sensitivity, accuracy, signal strength, or usable bandwidth.
• Rounding too early: Keep full precision through conversions and calculations, then round the displayed result to the precision you need.

The calculator uses only the two endpoints. It does not account for measurement uncertainty, guard bands, filter roll-off, spectral peaks, or different definitions of occupied bandwidth. For a measured or regulated signal, use the applicable instrument method or technical specification and report how the endpoints were obtained.

Frequently Asked Questions

How do you calculate the frequency range?
Subtract the lower frequency from the upper frequency: range width = f_high − f_low. Use the same unit for both values.

Is frequency range the same as bandwidth?
In basic calculations, bandwidth often means the difference between the upper and lower frequency limits. In engineering, “bandwidth” may have a more specific definition tied to a signal, filter, or measurement method, so check the context.

What is the frequency range from 2.4 GHz to 2.5 GHz?
It is 0.1 GHz, which equals 100 MHz or 100,000,000 Hz.

Can a frequency range start at 0 Hz?
Yes. The width can be calculated if the lower endpoint is zero. However, the upper-to-lower ratio cannot be calculated because division by zero is undefined.

How do I convert Hz to MHz?
Divide hertz by 1,000,000. For example, 900,000,000 Hz is 900 MHz.

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in low | Lower frequency | Hz | 100 | 0 | 1000000000000
in high | Upper frequency | Hz | 1000 | 0 | 1000000000000
out width | Frequency range | Hz | high - low + 0 * sqrt(high - low) | 2
out mid | Arithmetic midpoint | Hz | (low + high) / 2 | 2
out ratio | Upper-to-lower ratio | - | high / low + 0 * sqrt(low) | 3