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ENEnglish繁中繁體中文ESEspañolARالعربيةFRFrançaisITItalianoPTPortuguêsRUРусскийDEDeutschJA日本語VITiếng ViệtKO한국어THไทยTRTürkçe

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Engineering Calculator · 120

Water Vapor Transmission Rate Calculator

Calculate a water-vapor transmission rate from the corrected transmitted mass, exposed specimen area and measurement interval.

Pressure & environment
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Live calculation

Enter the known values.

Units remain visible beside every field and result. Change any input to recalculate immediately in your browser.

01

Inputs

02

Results

Water-vapor transmission rate10g/(m²·day)
Hourly area-normalized rate0.416667g/(m²·h)
Transmitted mass per hour0.004167g/h

Formula
WVTRday=ΔmA Δth 24\mathrm{WVTR}_{\mathrm{day}}=\frac{\Delta m}{A\,\Delta t_h}\,24

The calculation runs locally in this browser. Values are not submitted or stored by this tool.

Direct answer

What this result means

WVTR is transmitted water-vapor mass divided by exposed area and elapsed time. Transmitting 0.1 g through 0.01 m² in 24 hours gives 10 g/m²/day. Use a valid steady measurement interval and retain temperature, humidity and method; this does not predict water leakage through a complete enclosure.

Water Vapor Transmission Rate Calculator engineering relationship diagramThe input is corrected transmitted mass during a valid interval, not the total mass of a test cup or specimen. Hours are converted to days by multiplying the hourly area-normalized rate by 24. A test normally establishes the appropriate steady mass-change slope with multiple readings and method-specific corrections. This dedicated schematic represents wvtr cup area mass time and is not to scale.Exposed area AElapsed time ΔtCorrected vapor mass ΔmMEASURED MASS, AREA AND TIME · TOOL 120Corrected transmitted massWater-vapor transmission r…
Calculator-specific engineering relationship diagram — schematic, not a product drawing, and not to scale.

Formula & theory

Make the assumptions visible.

The input is corrected transmitted mass during a valid interval, not the total mass of a test cup or specimen. Hours are converted to days by multiplying the hourly area-normalized rate by 24. A test normally establishes the appropriate steady mass-change slope with multiple readings and method-specific corrections.

Calculation relationship
WVTRday=ΔmA Δth 24\mathrm{WVTR}_{\mathrm{day}}=\frac{\Delta m}{A\,\Delta t_h}\,24

The input is corrected transmitted mass during a valid interval, not the total mass of a test cup or specimen. Hours are converted to days by multiplying the hourly area-normalized rate by 24. A test normally establishes the appropriate steady mass-change slope with multiple readings and method-specific corrections.

Variables

ΔmCorrected water-vapor mass transmitted in the selected intervalg
AExposed transmission aream²
ΔthElapsed measurement intervalh

Use sequence

From measurement to review

  1. Identify the specimen, exposed area, method, temperature, humidity and valid steady measurement interval.
  2. Enter corrected transmitted mass, exposed area and elapsed hours.
  3. Report WVTR with those conditions and use partial vapor-pressure difference for a separate permeance calculation.

Limits

What this calculation does not confirm

  • The entered mass change represents water-vapor transport across the stated area; other mass changes and edge leakage have been addressed by the test.
  • A single interval normalization does not establish steady state or perform gravimetric corrections.
  • WVTR concerns vapor transport, not liquid-water ingress, complete-enclosure leakage or an IP rating.

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Calculate measured mass change and linear dimensional change after a defined conditioning or liquid-exposure procedure.

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Calculator FAQ

Use the number without losing the engineering context.

These answers clarify what the tool calculates and where a product-specific review still begins.

01Calculator guidanceWhat mass should I enter for a WVTR calculation?

Use the corrected water-vapor mass transmitted during the selected valid interval. Do not enter the full test-cup mass, an arbitrary specimen weight change or mass affected by uncorrected edge leakage.

02Calculator guidanceDoes low WVTR establish an enclosure IP rating?

No. Water-vapor diffusion and liquid-water ingress are different processes. IP classification concerns the complete tested enclosure under its specified procedure.

03Calculator guidanceCan WVTR values measured at different humidity or temperature be compared directly?

Only with a justified comparison model and compatible methods. Retain both-side humidity, temperature, specimen construction and test procedure; changing those conditions can change the reported rate.

Product selection support

Connect the calculation with cable-entry product options.

Bepto Cable Glands can help relate a preliminary result to the product family and current model information for your application. You can start with the details you have; a complete drawing package is not needed to ask a question.

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