Everything RF has a page dedicated to calculators for RF applications. These include:

• Conversion:
  dBm To Watt Calculator | Frequency to Wavelength | Noise Figure to Noise Temperature Calculator | Noise Temperature to Noise Figure Converter | Watt To dBm Calculator | Wavelength to Frequency
• Antenna Calculators:
  Antenna Downtilt Angle Calculator | Antenna Downtilt Coverage Calculator | Antenna Near Field Distance Calculator | EIRP - Effective Isotropic Radiated Power | Helical Antenna Design | Line of Sight Calculator | Microstrip Patch Antenna Calculator | Parabolic Antenna Gain Calculator
• Attenuator Calculators:
  Balanced Attenuator Calculator | Bridged Tee Attenuator Calculator | Pi Attenuator Calculator | Reflection Attenuator Calculator | Tee Attenuator Calculator
• Microstrip Calculators:
  Differential Microstrip Impedance Calculator | Differential Microstrip Impedance Calculator (Using Zo) | Embedded Microstrip Impedance Calculator | Microstrip Width Calculator | Transmission Line Mitred Bend Calculator
• Radar Calculators:
  Effective Antenna Aperture Calculator | Radar Blind Speed Calculator | Radar Range Equations and Calculator | RF Power Density | Target Gain Factor Calculator
• RF Calculators:
  Coax Calculator | Coaxial Cable Calculator |CRA Calculator |Directional Coupler Calculator |Free Space Path Loss Calculator | Fresnel Zone Calculator | Friis Transmission Calculator | IRA Calculator |Link Budget Calculator | MicroStrip Calculator | Minimum Detectable Signal Calculator | Noise Figure Calculator | Plane Wave Calculator | Power Divider Calculator | Resonant Frequency Calculator | RF Amplifier PAE Calculator | RF Transformer Calculator | SAR Calculator | SFDR Calculator | Skin Depth Calculator | TDR Calculator | Varactor Diode Calculator | VSWR Calculator | Wavelength Calculator | Wilkinson Power Divider Calculator
• Waveguide Calculators:
  Circular Waveguide Calculator | Waveguide Calculator