This calculator can be used to convert between Peak-to-Peak Voltage and Power.
The formula to convert VPP to dBm is
PdBm = 10*Log10((1/Z)*(Vpp/(2√2))2)
The impedance Z, will also need to be specified (default value is 50 ohm)
The calculator also provides VRMS where
VRMS = Vpp/(2√2)
- VRMS to Vpp
- PdBm to Vpp