EMC & RF Calculators
38 free calculators for dB and unit conversion, RF and transmission lines, testing and measurement, shielding and filters. Everything runs in your browser.
dB & Unit Conversion
dBm ↔ Watt Power Converter
Convert between dBm, mW and W. 0 dBm = 1 mW and 30 dBm = 1 W.
dB & Unit ConversiondBµV ↔ Volt Converter
Convert between dBµV, µV and V. 60 dBµV = 1 mV.
dB & Unit ConversiondBµV/m ↔ V/m Field Strength Converter
Convert field strength between dBµV/m, mV/m and V/m so you can compare emission limits with immunity test levels.
dB & Unit ConversiondBm ↔ dBµV Converter (with Impedance)
Convert between dBm and dBµV for a given impedance. At 50 Ω, dBµV = dBm + 107.
dB & Unit ConversiondB ↔ Ratio Converter (Power/Voltage)
Convert dB to power ratio and voltage (field) ratio, and back. 20 dB = 10× voltage, 100× power.
dB & Unit ConversiondB Level Summation (Uncorrelated Signals)
Add two uncorrelated signal levels in dB by summing their powers. Equal levels give +3 dB.
dB & Unit ConversionE-field → Power Density & H-field
Convert electric field E (V/m) to power density (W/m², mW/cm²) and magnetic field H (A/m).
dB & Unit ConversionMagnetic Field Unit Converter (A/m ↔ µT ↔ dBpT ↔ dBµA/m)
Convert magnetic field strength (A/m), flux density (µT, mG) and levels (dBpT, dBµA/m). Editing any box updates the others instantly.
RF & Transmission Lines
VSWR ↔ Return Loss ↔ Reflection Coefficient
Convert between VSWR, return loss, reflection coefficient and mismatch loss. Edit any field and the others update.
RF & Transmission LinesFree-Space Path Loss & Friis Received Power
Free-space path loss from frequency and distance, plus received power via the Friis equation.
RF & Transmission LinesFrequency ↔ Wavelength (with λ/2, λ/4)
Convert between frequency and wavelength and get λ/2 and λ/4 lengths, optionally in a dielectric medium.
RF & Transmission LinesFar-Field Distance Calculator
Far-field boundary 2D²/λ and reactive near-field boundary λ/2π from frequency and maximum antenna/EUT dimension.
RF & Transmission LinesAntenna Factor (AF) ↔ Antenna Gain
Convert between antenna factor (AF, dB/m) and antenna gain (dBi) at a given frequency (50 Ω, free space).
RF & Transmission LinesCable Loss Frequency Scaling (√f Approximation)
Estimate cable loss at another frequency from one known point using a √f approximation.
RF & Transmission LinesSignal Level Budget (Cascaded Gain/Loss)
Accumulate stage gains and losses in dB to get the output level of a signal chain.
RF & Transmission LinesCoaxial Cable Characteristic Impedance
Characteristic impedance, velocity factor and capacitance per metre of a coaxial line from its diameters and dielectric constant.
RF & Transmission LinesInductor/Capacitor Reactance & Resonance
Reactance of an inductor and capacitor at a given frequency, plus the LC resonant frequency.
RF & Transmission LinesRise Time → Bandwidth & Knee Frequency
Estimate signal bandwidth (0.35/tr) and knee frequency (0.5/tr) from the rise time.
RF & Transmission LinesTrapezoidal Pulse Spectrum Envelope (Clock Harmonics)
Spectrum envelope of a trapezoidal clock pulse from amplitude, frequency, pulse width and rise time: both corner frequencies and the harmonic envelope level at a frequency of interest.
RF & Transmission LinesAttenuator Pad (π and T) Resistor Calculator
Resistor values for T and π attenuator pads from the required attenuation in dB and the system impedance.
Testing & Measurement
Measured Voltage → Field Strength (dBµV/m)
Field strength in dBµV/m from receiver reading, antenna factor, cable loss, attenuator and preamp gain.
Testing & MeasurementTest Distance Conversion (Limit 3 m ↔ 10 m)
Convert limits or readings between test distances. 10 m → 3 m is about +10.46 dB.
Testing & MeasurementCombined & Expanded Uncertainty (RSS)
Combine up to five standard-uncertainty contributions by RSS and multiply by the coverage factor for expanded uncertainty.
Testing & MeasurementUncertainty Distribution Divisor (Rectangular, Triangular…)
Convert a ± half-width into a standard uncertainty using the divisor for rectangular, triangular, U-shaped or normal distributions.
Testing & MeasurementLimit Margin & Uncertainty Check
Compute the margin between a measured value and the limit, and check whether it holds after adding expanded uncertainty.
Testing & MeasurementReceiver Noise Floor Calculator
Theoretical noise floor (dBm, dBµV) from RBW and receiver noise figure.
Testing & MeasurementStepped Scan Duration Calculator
Number of points and total time of a stepped scan from frequency range, step size and dwell time.
Testing & MeasurementRadiated Immunity Required Power (V/m → W)
Estimate the amplifier power needed for radiated-immunity testing from target field, distance and antenna gain, including 80 % AM.
Testing & MeasurementCurrent Probe dBµV ↔ dBµA Conversion
Convert receiver dBµV readings to conductor current in dBµA using the probe transfer impedance in dBΩ.
Testing & MeasurementPCB Loop (Differential-Mode) Radiated Field Estimate
Estimate the maximum radiated field from a PCB differential-mode loop from frequency, loop area, loop current and distance.
Testing & MeasurementCable Common-Mode Current Radiated Field Estimate
Estimate the maximum radiated field of a cable from frequency, cable length, common-mode current and distance.
Shielding & Filters
Shielding Effectiveness / Insertion Loss from Readings
Shielding effectiveness or filter insertion loss from before/after readings, with attenuation ratio and transmitted-power percentage.
Shielding & FiltersSkin Depth & Absorption Loss
Skin depth and absorption loss for a given thickness from frequency, conductivity and permeability. Copper at 1 MHz is about 66 µm.
Shielding & FiltersRC Low-Pass Filter Cutoff & Attenuation
Cutoff frequency, time constant and attenuation at a chosen frequency for an RC low-pass filter.
Shielding & FiltersLC Filter Resonance & Characteristic Impedance
Resonant (natural) frequency and characteristic impedance of an LC filter, computed in one step from the inductance L and capacitance C.
Shielding & FiltersSlot / Aperture Shielding Effectiveness Estimate
Estimate the shielding effectiveness of an aperture from frequency and the longest dimension of the opening, including the reduction for multiple identical openings and the leakage onset frequency.
Shielding & FiltersVent / Honeycomb Waveguide-Below-Cutoff Shielding
Compute cutoff frequency and waveguide-below-cutoff shielding for vent or honeycomb openings from their size and depth.
Shielding & FiltersMetal Enclosure Cavity Resonance (Rectangular Box)
Find the four lowest resonant frequencies of a rectangular metal enclosure from its width, depth and height.
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