Unit Conversion with SciPy

The scipy.constants module in SciPy provides a comprehensive collection of predefined constants for unit conversions. These constants are invaluable for ensuring precision and consistency when working with measurements across various scientific and engineering disciplines. By utilizing these built-in values, you can significantly minimize errors associated with manual unit conversions.

This guide details the key unit conversion constants available in SciPy, along with practical examples of their usage.

General Usage

The general pattern for using these constants involves importing the specific constant from scipy.constants and then multiplying or dividing your value by it to perform the conversion.

from scipy.constants import <constant_name>

# Perform conversion
converted_value = original_value * <constant_name>
# or
converted_value = original_value / <constant_name>

Length Conversion

SciPy offers constants for converting lengths between meters and various other units.

Key Length Conversion Constants

• Inch to Meter (inch): 1 inch = 0.0254 meters

  from scipy.constants import inch
  
  inches = 10
  meters = inches * inch
  print(f"{inches} inches is equal to {meters} meters")

  Output:

  10 inches is equal to 0.254 meters

• Foot to Meter (foot): 1 foot = 0.3048 meters

  from scipy.constants import foot
  
  feet = 10
  meters = feet * foot
  print(f"{feet} feet is equal to {meters} meters")

  Output:

  10 feet is equal to 3.048 meters

• Yard to Meter (yard): 1 yard = 0.9144 meters

  from scipy.constants import yard
  
  yards = 10
  meters = yards * yard
  print(f"{yards} yards is equal to {meters} meters")

  Output:

  10 yards is equal to 9.144 meters

• Light Year to Meter (light_year): 1 light year ≈ 9.4607 × 10¹⁵ meters

  from scipy.constants import light_year
  
  ly = 1
  meters = ly * light_year
  print(f"{ly} light year is equal to {meters} meters")

  Output:

  1 light year is equal to 9460730472580800.0 meters

Additional Length Units

SciPy also includes constants for:

• parsec (parsec)
• astronomical_unit (AU)
• And more.

Mass Conversion

SciPy's mass conversion constants facilitate conversions between kilograms (the SI base unit) and other common mass units.

Key Mass Conversion Constants

• Gram to Kilogram (gram): 1 gram = 0.001 kilograms

  from scipy.constants import gram
  
  grams = 1000
  kilograms = grams * gram
  print(f"{grams} grams is equal to {kilograms} kilograms")

  Output:

  1000 grams is equal to 1.0 kilograms

• Metric Ton to Kilogram (metric_ton): 1 metric ton = 1000 kilograms

  from scipy.constants import metric_ton
  
  tons = 10
  kilograms = tons * metric_ton
  print(f"{tons} metric tons is equal to {kilograms} kilograms")

  Output:

  10 metric tons is equal to 10000.0 kilograms

Other Mass Units

Other available mass constants include:

• pound (pound)
• ounce (ounce)
• atomic_mass (atomic mass unit)
• carat (carat)
• grain (grain)

Time Conversion

Easily convert between seconds, minutes, hours, days, weeks, and years using SciPy's time constants. Each constant represents the number of seconds in the respective time unit.

Key Time Conversion Constants

• Hour (hour): 1 hour = 3600 seconds

  from scipy.constants import hour
  
  print(f"1 hour is equal to {hour} seconds.")

  Output:

  1 hour is equal to 3600.0 seconds.

• Day (day): 1 day = 86400 seconds

  from scipy.constants import day
  
  days = 1
  seconds = days * day
  print(f"{days} day is equal to {seconds} seconds")

  Output:

  1 day is equal to 86400.0 seconds

Additional Time Units

Additional time constants include:

• minute (minute)
• week (week)
• year (year)
• Julian_year (Julian year)

Temperature Conversion

SciPy simplifies temperature scale conversions between Celsius, Kelvin, and Fahrenheit using these constants.

Key Temperature Conversion Constants

• Zero Celsius in Kelvin (zero_Celsius): This constant represents the offset to convert Celsius to Kelvin. The formula is K = C + zero_Celsius.

  from scipy.constants import zero_Celsius
  
  celsius_temp = 25
  kelvin_temp = celsius_temp + zero_Celsius
  print(f"{celsius_temp} °C is equal to {kelvin_temp} K")

  Output:

  25 °C is equal to 298.15 K

• Degree Fahrenheit to Celsius (degree_Fahrenheit): This constant is the multiplier used in the Fahrenheit to Celsius conversion formula: (°F - 32) * degree_Fahrenheit = °C.

  from scipy.constants import degree_Fahrenheit
  
  fahrenheit_temp = 77
  celsius_temp = (fahrenheit_temp - 32) * degree_Fahrenheit
  print(f"{fahrenheit_temp} °F is equal to {celsius_temp} °C")

  Output:

  77 °F is equal to 25.0 °C

Energy Conversion

Convert various energy units such as electron volts, calories, and joules precisely with SciPy’s energy constants.

Key Energy Conversion Constants

• Electron Volt to Joules (eV): 1 eV = 1.602176634 × 10⁻¹⁹ joules

  from scipy.constants import eV
  
  energy_eV = 1
  energy_J = energy_eV * eV
  print(f"{energy_eV} eV is equal to {energy_J} J")

  Output:

  1 eV is equal to 1.602176634e-19 J

• Calorie to Joules (calorie): 1 calorie = 4.184 joules

  from scipy.constants import calorie
  
  energy_cal = 1
  energy_J = energy_cal * calorie
  print(f"{energy_cal} cal is equal to {energy_J} J")

  Output:

  1 cal is equal to 4.184 J

Other Energy Units

Other energy units available include:

• Btu (British Thermal Unit)
• Hartree (Hartree energy)
• kWh (kilowatt-hour)
• And more.

Pressure Conversion

SciPy’s pressure constants facilitate conversions between pascals (the SI unit) and other common pressure units.

Key Pressure Conversion Constants

• Atmosphere to Pascal (atmosphere): 1 atm = 101,325 pascals

  from scipy.constants import atmosphere
  
  pressure_pa = 2 * atmosphere
  print(f"2 atmospheres is equal to {pressure_pa} Pa")

  Output:

  2 atmospheres is equal to 202650.0 Pa

• Bar to Pascal (bar): 1 bar = 100,000 pascals

  from scipy.constants import bar
  
  pressure_pa = 1.5 * bar
  print(f"1.5 bar is equal to {pressure_pa} Pa")

  Output:

  1.5 bar is equal to 150000.0 Pa

Other Pressure Units

Other pressure units available include:

• torr (torr)
• mmHg (millimeter of mercury)
• psi (pounds per square inch)

Power Conversion

Convert power units such as watts, horsepower, and erg per second with ease.

Key Power Conversion Constants

• Horsepower to Watt (horsepower): 1 hp ≈ 745.7 watts

  from scipy.constants import horsepower
  
  power_hp = 1
  power_watt = power_hp * horsepower
  print(f"{power_hp} hp is equal to {power_watt} watts")

  Output:

  1 hp is equal to 745.6998715822701 watts

• Erg per Second to Watt (erg): 1 erg/s = 1e-07 watts

  from scipy.constants import erg
  
  print(f"1 Erg per second is equal to {erg} Watts")

  Output:

  1 Erg per second is equal to 1e-07 Watts

Volume Conversion

Easily convert volumes between cubic meters (the SI unit) and other common volume units.

Key Volume Conversion Constants

• Liter to Cubic Meter (litre): 1 liter = 0.001 cubic meters

  from scipy.constants import litre
  
  cubic_meters = 2
  liters = cubic_meters / litre
  print(f"{cubic_meters} cubic meters is equal to {liters} liters")

  Output:

  2 cubic meters is equal to 2000.0 liters

• Gallon to Cubic Meter (gallon): 1 gallon ≈ 0.00378541 cubic meters

  from scipy.constants import gallon
  
  cubic_meters = 0.01
  gallons = cubic_meters / gallon
  print(f"{cubic_meters} cubic meters is equal to {gallons} gallons")

  Output:

  0.01 cubic meters is equal to 2.6417205235814842 gallons

Other Volume Units

Other volume units available include:

• inch**3 (cubic inch)
• foot**3 (cubic foot)
• And more.

Conclusion

The scipy.constants module offers a powerful, accurate, and user-friendly set of unit conversion constants. By leveraging these predefined values, scientists, engineers, and developers can ensure consistency and precision in their calculations across numerous measurement domains, simplifying workflows and reducing the likelihood of manual conversion errors.