Define the purchasing question
Area-unit conversion makes barrier results easier to read but cannot make observations from different conditions comparable.
Use the OTR and WVTR tools only to change reporting area for the same observation. Ask the supplier for matching-condition test results before comparing barriers.
Collect measurements that match the calculation
Retain the complete unit including time basis, test temperature, humidity, gas and pressure conditions, method, film thickness and specimen details. Use matching source conditions for comparisons.
Convert only reporting area for the same observation. Keep temperature, humidity, pressure, gas conditions, specimen and method unchanged. This is not a conversion between different test conditions.
- Measured transmission per m² per day (cm³/m²/day)
Work through an illustrative case
Per 100 in²/day = Per m²/day × 0.064516
10 cm³/m²/day becomes 0.64516 cm³/100 in²/day.
Replace these illustrative inputs with measured data or a quotation for the same scope. Change one assumption at a time so that a difference can be traced to a dimension, quantity, charge or process change.
Avoid the expensive comparison error
A numerical area conversion cannot translate a WVTR measured at one humidity into another, or derive shelf life from OTR. Permeability and transmission rate are also different quantities.
- Same specimen and test conditions required.
- No permeability, barrier lifetime or shelf-life prediction.
Common questions
What should I verify before using this result?
Retain the complete unit including time basis, test temperature, humidity, gas and pressure conditions, method, film thickness and specimen details. Use matching source conditions for comparisons.
Does this calculation approve the packaging?
No. It estimates only the stated quantity, conversion or cost boundary. Technical performance and any required test or supplier approval remain separate.