Radar Equation Calculator
Use this tool to estimate either received power at a known range or maximum detection range from a sensitivity threshold.
Pr = (Pt G2 λ2 σ) / ((4π)3 R4 L)
What this radar equation calculator does
This calculator applies the classic monostatic radar equation to estimate how strong a reflected radar signal is at the receiver, or how far a target can be detected for a given sensitivity. It is useful for quick link-budget style checks when comparing power, gain, frequency, target size, and range.
Inputs and what they mean
Core radar parameters
- Transmit Power (Pt): RF power sent by the radar transmitter in watts.
- Antenna Gain (G): Directional amplification of the antenna in dBi (converted internally to linear gain).
- Frequency: Used to compute wavelength λ, where λ = c/f.
- Target RCS (σ): Radar cross section in square meters; larger values generally reflect more energy.
- System Losses (L): Combined losses (feedline, radome, processing, mismatch), entered in dB.
Mode-specific input
- Received Power mode: Requires known range R.
- Maximum Range mode: Requires minimum detectable signal Smin.
Why range is so sensitive
In free space, received power scales with 1/R4 for monostatic radar. That means even modest increases in distance can dramatically reduce return signal strength. This is why antenna gain, coherent integration, pulse compression, and low-noise receiver design are so critical in practical radar systems.
Example interpretation
Suppose you use 1 kW transmit power, 30 dBi gain, 10 GHz frequency, 1 m² target RCS, and 6 dB losses. If you compute received power at 50 km, the returned value is often extremely small in watts but easier to interpret in dBm. Engineers usually compare that dBm value to the receiver noise floor and detection threshold to estimate probability of detection.
Important assumptions and limitations
- Assumes line-of-sight propagation and ideal free-space behavior.
- Assumes a monostatic configuration (same antenna for transmit and receive).
- Does not include clutter, multipath, ducting, atmospheric absorption detail, or jamming.
- Uses a single RCS value, while real targets have aspect-dependent and fluctuating RCS.
- Does not model CFAR logic, integration gain, scan loss, or dwell-time constraints.
Tips for better practical estimates
- Add realistic margin in system losses for implementation effects.
- Use conservative RCS assumptions for worst-case target aspect.
- Pair radar equation output with receiver noise calculations (kTB + NF).
- Validate against measured field data whenever possible.
Quick FAQ
Is this for search radar or tracking radar?
Either, as a first-order estimate. Operational performance still depends on scan strategy, dwell time, and processing.
Why are both watts and dBm shown?
Watts are physically intuitive, while dBm is the standard engineering scale for comparing to receiver thresholds and noise budgets.
Can gain or losses be entered in linear units?
This tool accepts dBi and dB only, then converts internally to linear quantities required by the equation.