Protein calculator

Per kg of body weight (or lean mass, if you know your bodyfat). The range widens for lifters and tightens for sedentary adults. Numbers below come from the most-cited reviews and meta-analyses on protein dose and resistance training:

Sedentary, maintaining        0.8 - 1.2 g/kg   (RDA floor to comfortably above)
Active, no resistance work    1.2 - 1.4 g/kg   (Phillips & Van Loon, 2011)
Lifting + cutting             1.6 - 2.2 g/kg   (Helms et al., 2014)
Lifting, maintaining/building 1.6 - 2.0 g/kg   (Morton et al., 2018)
Endurance athlete             1.4 - 1.7 g/kg   (Phillips & Van Loon, 2011)
Over 65, sarcopenia risk      1.0 - 1.2 g/kg   (Bauer et al., 2013 / PROT-AGE)

If you know your bodyfat percentage, the calculator switches to lean body mass (LBM). Muscle is metabolically active; fat mass is not. Higher bodyfat individuals don't need protein for the fat. The conversion:

LBM        = weight × (1 - bodyfat%/100)
protein_g  = LBM_kg × g_per_kg_lean
(equivalent ranges are roughly 1.5-2.5 g/kg LBM)

Distribution matters too. Muscle protein synthesis (MPS) responds to single boluses of around 0.3-0.4 g/kg, with the response plateauing past that. Three to five meals at that dose maximises 24-hour MPS more reliably than one big bolus and a couple of tiny ones (Schoenfeld & Aragon, 2018). The plant-eating wrinkle: lower leucine content per gram, so totals should be on the higher end of the range.

The RDA caveat. The 0.8 g/kg figure your doctor's chart shows is thenitrogen-balance minimum to not be deficient. It was never meant as an optimisation target. Modern indicator amino acid oxidation (IAAO) studies have argued the RDA itself is under-estimated and should sit closer to 1.0-1.2 g/kg even for sedentary adults (Elango et al., 2010).