Metrics Conversion. METS vs Watts

I am looking for conversion apps or formulae for converting METS , Watts and mVO2.
Many medical papers are based on units that I am having troule getting conversions.
Specifically I have a need to be able to convert for cardiac rehab based equipment.
I realize variation in being based on weight and time , but my conversions are getting errors that I am having trouble tracking

One calorie per 2.2 pounds of body weight per hour is 1 MET.

Powermeters want to read in Watts and the Watts to Mets relationship and conversion is throwing me .
When I use:
Multiply Watts by 0.0143 to get kcal/min.
Divide kcal/min by 5.05 to get litres of O2/min.
Divide litres of O2/min by bodyweight in kg (pounds ÷ 2.2) to get mL/kg/min.
Divide mL O2/kg/min by 3.5 to get METs.
I am getting 0.0010470089 METS for 100w
And am having trouble finding my error

Using an online calculator with 100w 170lbs 10 min I get 6 METS which seems about right

At least two errors. One

Divide litres of O2/min by bodyweight in kg (pounds ÷ 2.2) to get mL/kg/min

You’re off by a factor of 1000 here.

Two, you’re using powermeter output and not accounting for metabolic efficiency. Usually this is ballparked at about 25%, so you need to multiply by 4. This gives about 4.2 METs for your 100w 170lbs. It appears the standard for defining METs (17.5W = 1 MET = 1.22kcal/minute for a 70kg person) assumes an efficiency of more like 20%, which is the rest of the difference.

Because efficiency is more like 20 % :wink:
See, e.g., DOI: 10.1055/s-2004-815848