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Engineering Calculator · 039

Relative Humidity from Dew Point Calculator

Estimate relative humidity from dry-bulb air temperature and dew-point temperature using the Magnus relationship.

Pressure & environment
Start calculationReview the method

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

Estimated relative humidity52.56%
Air-to-dew-point spread10°C
Relative vapour ratio0.5256:1

Formula
RHT,Td=100exp⁡ ⁣[aTdb+Td−aTb+T]RH_{T,T_d}=100\exp\!\left[\frac{aT_d}{b+T_d}-\frac{aT}{b+T}\right]

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

Direct answer

What this result means

Estimate relative humidity from dry-bulb air temperature and dew-point temperature using the Magnus relationship. The relationship RH = 100 es(Td) / es(T) ties air temperature and dew-point temperature directly to the reported result. Air and dew-point temperatures are expressed in degrees Celsius. Treat the value as a transparent preliminary calculation, then compare it with the actual cable-entry assembly and current product documentation.

Relative Humidity from Dew Point Calculator engineering relationship diagramRH = 100 es(Td) / es(T) defines the calculation shown here. Air and dew-point temperatures are expressed in degrees Celsius. Keep the entered units with the result so another reviewer can reproduce the method. This dedicated schematic represents relative humidity from dew point and is not to scale.HUMIDITY ESTIMATE · TOOL 039Air temperatureEstimated relative humidity
Calculator-specific engineering relationship diagram — schematic, not a product drawing, and not to scale.

Formula & theory

Make the assumptions visible.

RH = 100 es(Td) / es(T) defines the calculation shown here. Air and dew-point temperatures are expressed in degrees Celsius. Keep the entered units with the result so another reviewer can reproduce the method.

Calculation relationship
RHT,Td=100exp⁡ ⁣[aTdb+Td−aTb+T]RH_{T,T_d}=100\exp\!\left[\frac{aT_d}{b+T_d}-\frac{aT}{b+T}\right]

RH = 100 es(Td) / es(T) defines the calculation shown here. Air and dew-point temperatures are expressed in degrees Celsius. Keep the entered units with the result so another reviewer can reproduce the method.

Formula terms

Variables

TAir temperature°C

Use sequence

From measurement to review

  1. Confirm air temperature and dew-point temperature from a controlled drawing, measurement or project document.
  2. Apply RH = 100 es(Td) / es(T) with consistent units and keep the entered values beside the result.
  3. Use estimated relative humidity only after checking sensor accuracy, pressure range, representative ambient conditions and the limits of the Magnus approximation.

Limits

What this calculation does not confirm

  • Air and dew-point temperatures are expressed in degrees Celsius.
  • Inputs describe one defined operating or measurement condition and use mutually consistent units.
  • The result does not by itself confirm product suitability, standards compliance, ingress performance or installation approval.

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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 guidanceHow does the relative humidity from dew point calculator calculate estimated relative humidity?

The tool applies RH = 100 es(Td) / es(T) to air temperature, dew-point temperature. Air and dew-point temperatures are expressed in degrees Celsius. Keep the displayed units with the result so the calculation can be repeated.

02Calculator guidanceWhat does estimated relative humidity show for this humidity estimate review?

Estimate relative humidity from dry-bulb air temperature and dew-point temperature using the Magnus relationship. It is a preliminary engineering value, not confirmation of a cable-gland model, standards compliance or installation approval.

03Calculator guidanceWhat should be checked about sensor accuracy before using the relative humidity from dew point calculator result?

The equation does not model sensor accuracy, pressure range, representative ambient conditions and the limits of the Magnus approximation. Confirm those conditions against the actual cable-entry assembly, applicable requirement and current product documentation.

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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