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Trades & Professional Tools · HVAC

Duct Fitting Pressure Loss Calculator

Calculate fitting pressure loss from entered loss coefficient and velocity pressure.

Trades & Professional Tools · HVAC

Enter your project measurements

Measured inputs · visitor-entered product and design assumptions
  1. 1EnterProvide the known values
  2. 2CalculateResults update automatically
  3. 3VerifyReview the details and units
Try an example

Use one consistent unit basis and measurements taken at the stated locations and operating condition. Enter project, manufacturer, fluid-property, pressure-temperature, efficiency, and test criteria from the actual system. Values stay in this browser.

Trade calculator result

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Enter valid values to see the result.

Your entries are calculated in this browser and are not submitted to 365CALCS.COM.

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Understand the result

What the Duct Fitting Pressure Loss is for

Calculate fitting pressure loss from entered loss coefficient and velocity pressure.

A fan must move the required airflow through the whole air path. Straight duct, fittings, filters, coils, terminals, and measurement locations all affect the pressure picture.

At a glance

See the HVAC relationship

Fitting loss coefficient KAir density (kg/m³)Reference velocity (m/s)

The relationship

The formula used here

Δp=K·ρv²/2.

This calculator applies that relationship to your entries. Use the formula to check that the units, reference condition, and measurement location make sense together.

Field reading

Use the result as a next check

1. Describe one real condition

Enter values from the same system state, period, unit basis, and measurement location.

2. Read the relationship

Keep airflow, dimensions, density, pressure reference, and fitting data on the same basis. Then use the result to locate the next pressure or balance check.

3. Keep the boundary clear

It does not select duct sizes, fans, terminals, filters, controls, or prove sound, leakage, code, or installed balancing performance.

Quick guide

How to use this calculator

  1. Choose the calculation mode or measurement system that matches the values you actually have.
  2. Enter measured project dimensions and use product-specific coverage, density, yield, resistance, or waste data where requested.
  3. Review the intermediate results before ordering material or applying the result on site.

Calculation method

Calculation method

Δp=K·ρv²/2.

The calculator preserves full internal precision and rounds only displayed results. Quantity outputs round up when whole purchasable pieces are required.

Worked example

Worked example

K=0.4 at 5 m/s and 1.2 kg/m³ gives 6 Pa.

Δp=K·ρv²/2.

Supported inputs

Precision and limits

HVAC design and service boundary

HVAC results use the measured, design, manufacturer, psychrometric, fluid-property, pressure-temperature, efficiency, and test values you enter. They do not perform or certify Manual J, D, or S procedures; supply ventilation or code defaults; select equipment; identify refrigerant; determine a safe charge; authorize combustion, pressure, electrical, or refrigerant work; or replace approved manufacturer data and a qualified HVAC professional.

Planning scope

This calculator supports measurement, estimating, and scenario planning. It does not inspect a site, select a product, certify a design, or replace drawings, specifications, manufacturer instructions, local codes, permits, or a qualified trade professional.

Measured and product-specific inputs

Nominal dimensions can differ from actual dimensions. Verify inside pipe diameters, actual lumber sizes, product coverage, bag yield, material density, conductor resistance, waste, and packaging against the materials used on the project.

Safety and regulatory limits

Electrical, HVAC, structural, excavation, roofing, pressure, lifting, and life-safety work may require jurisdiction-specific calculations and professional approval. Do not use a generic planning result as a code-compliance or safety determination.

Precision and privacy

Inputs accept bounded plain decimals. Calculations remain in this browser and raw entered project values are not submitted to 365CALCS.COM.

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