convert Fahrenheit to Celcius and back, inches to feet and back, and Kg to Lbs and back

def convert(amount, from_unit, to_unit):
  from_to = {
    'fahrenheit': {
      'celcius': (amount - 32) * 5/9,
      'kelvin': (amount + 459.67) * 5/9
    },
    'celcius': {
      'fahrenheit': amount * 9/5 + 32,
      'kelvin': amount + 273.15
    },
    'kelvin': {
      'celcius': amount - 273.15,
      'fahrenheit': amount * 9/5 - 459.67
    },
    'inches': {
      'feet': amount * 0.0833333,
      'meters': amount * 0.0254
    },
    'feet': {
      'inches': amount * 12,
      'meters': amount * 0.3048
    },
    'meters': {
      'inches': amount * 39.3701,
      'feet': amount * 3.28084
    },
    'pounds': {