This Ham Radio Math Toolkit is a set of browser-based calculators for amateur radio operators who want fast, reliable answers without bouncing between separate pages or spreadsheets. It is designed to make common RF and antenna math easier, whether you are planning an antenna, checking coax characteristics, estimating signal loss, or converting between power and decibel values. This is helpful for both the field and the bench.
Use the band picker for common frequencies or type your own values. Results are browser-side estimates and starting points, so verify final cuts, losses, and ratings against the exact cable sheet, handbook, or manufacturer data before committing hardware.
Antenna, RF, and utility calculators in a layout that matches your newer hobby tools
This redesigned page keeps the same practical calculator mix while moving the toolkit into a fuller card-based layout with a sidebar, section navigation, expandable tool panels, and clearer results.
Everything runs locally in the browser. It is intended as a quick reference for common amateur radio calculations so you can move between antenna work, coax questions, power conversions, reactance, and SWR checks without jumping across separate pages.
Quick band picker
Pick a common amateur band center frequency, then push it into all calculator frequency fields or only the ones that are still blank.
Band selection
Included center frequencies
Antenna lengths
Common wire starting-point calculations. The classic amateur constants below are adjusted by the shortening factor to account for end effect, insulation, nearby objects, and real-world installation differences.
Inputs
Results
Formulas
Half-wave dipole (total) ≈ 468 / f(MHz)Quarter-wave ≈ 234 / f(MHz)Full-wave loop circumference ≈ 1005 / f(MHz)- Each result is then multiplied by the selected shortening factor.
Coax electrical length
Compute physical coax length for a desired electrical length, either in degrees or in fractions of a wavelength, using a selected or custom velocity factor.
Inputs
Results
Formulas
λ(coax) = (c / f) × VFLength = λ × (degrees / 360)Length = λ × fractionc = 299,792,458 m/s
Coax loss
Uses embedded typical attenuation curves and interpolates between table points. This is best for quick planning and sanity checks, not as a substitute for the exact datasheet of the exact cable revision in hand.
Inputs
Results
--
Free-space path loss (FSPL)
A quick link-budget sanity check for ideal free-space conditions. Real-world paths also depend on terrain, clutter, antenna patterns, feedline losses, fade margin, polarization, and local noise floor.
Inputs
Results
FSPL = 32.44 + 20log10(fMHz) + 20log10(dkm)Power & dB
Convert between watts, dBm, and dBW; estimate RMS and peak-to-peak voltage at a given impedance; compare two power levels in dB; and convert antenna gain between dBd and dBi.
Power conversion
dB difference
10 × log10(P2 / P1)P2 / P1.Antenna gain conversion
Editing either field updates the other using dBi = dBd + 2.15.
Formulas
dBm = 10 × log10(P(W) × 1000)dBW = 10 × log10(P(W))VRMS = √(P × Z)Vpp = 2 × √2 × VRMSdBi = dBd + 2.15
Reactance & resonance
Useful for LC networks, traps, loading components, and basic tuning intuition.
Inputs
Results
Formulas
XL = 2πfLXC = -1 / (2πfC)f0 = 1 / (2π√(LC))- Use
fin Hz,Lin henries, andCin farads.
SWR / Return loss
Two paths are included: estimate from forward and reflected power, or calculate from load impedance relative to a system impedance Z0.
Inputs
Results
--
Formulas
|Γ| = √(Pref / Pfwd)SWR = (1 + |Γ|) / (1 - |Γ|)Return Loss (dB) = -20 × log10(|Γ|)Mismatch Loss (dB) = -10 × log10(1 - |Γ|²)Γ = (ZL - Z0) / (ZL + Z0)
Sources
Coax velocity factor and loss data below are embedded as typical planning values. Always verify your exact cable, connector family, and frequency range against the specific manufacturer datasheet for the exact part you are using.
Embedded public reference links
General notes
- SWR, return loss, free-space path loss, reactance, resonance, and dB conversions use standard RF engineering relationships commonly found in amateur radio handbooks and introductory electromagnetics references.
- Antenna length outputs are starting points, not promises. Nearby objects, insulation, end effect, and installation geometry can shift a real antenna away from the idealized values shown here.
- Loss tables are especially approximate at the high and low ends of each product family. Treat them as planning data unless you have the exact cable sheet in hand.