Temperature Interval Unit Converter in Excel

From To

1.8

Add-in Formula =PO.UnitConverter(1, "deltaC", "deltaF")

Excel Lambda

=LAMBDA(x,
  LET(
    ratio, 1.8,
    x * ratio
  )
)(1)

Category Lambda

=LAMBDA(x, from, to,
  LET(
    f, SWITCH(from,
      "deltaK", 1,
      "deltaC", 1,
      "deltaF", 0.555555555555556,
      "deltaR", 0.555555555555556),
    t, SWITCH(to,
      "deltaK", 1,
      "deltaC", 1,
      "deltaF", 0.555555555555556,
      "deltaR", 0.555555555555556),
    x * f / t
  )
)(1, "deltaC", "deltaF")

How to save as a reusable Excel function

LAMBDA is a built-in Excel feature (Microsoft 365) that lets you create custom functions without VBA. The formulas above work as-is when pasted into a cell.

To save a LAMBDA as a reusable named function:

Go to Formulas → Name Manager → New
Enter a name, e.g. ConvertTemperatureInterval
In Refers to, paste the LAMBDA formula without the trailing invocation (...)
Click OK

Now use =ConvertTemperatureInterval(1, "deltaC", "deltaF") anywhere in your workbook — no add-in required.

Conversion Factors (base: deltaK)

Unit	Name	Factor
deltaK	delta kelvin	1
deltaC	delta Celsius	1
deltaF	delta Fahrenheit	0.555555555555556
deltaR	delta Rankine	0.555555555555556