1 · Identify each source
List the machine, dust or fume, hood/opening dimensions, source-to-hood distance and whether heat or moving parts throw contaminants into the air.
7US ENGINEERING TOOLS · FREE TO USE
Free Engineering Tools for Dust Collection & HVAC
Estimate extraction airflow, check heating and cooling loads, and convert engineering units. Free tools with clear formulas, worked examples and practical guidance.
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Airflow Unit Converter
CFM to m³/h, CMH to CFM, L/s and more.
1 CFM = 1.69901079552 m³/h. CMH means m³/h.
This converts volume-flow units at the same reference conditions. It does not convert actual flow to standard or normal flow (ACFM, SCFM or Nm³/h).
Results rounded to eight significant digits. For reference only — verify before use.
| Unit | Value |
|---|---|
| m³/h (CMH) | 10,000 |
| CFM (ft³/min) | 5,885.7778 |
| L/s | 2,777.7778 |
| m³/min | 166.66667 |
| m³/s | 2.7777778 |
| L/min | 166,666.67 |
Pressure Unit Converter
Fan pressure, filter differential pressure and compressed-air supply units.
1 bar = 100,000 Pa. 1 mmH₂O = 9.80665 Pa. 1 conventional inH₂O ≈ 249.0889 Pa.
Signed values are supported. Unit conversion preserves the pressure reference: gauge, absolute or differential. It does not change one reference into another. Water-column factors vary with the stated convention or temperature.
Results rounded to eight significant digits. For reference only — verify before use.
| Unit | Value |
|---|---|
| Pa | 2,500 |
| kPa | 2.5 |
| mmH₂O (conventional) | 254.92905 |
| inH₂O (conventional) | 10.036577 |
| mbar | 25 |
| bar | 0.025 |
| MPa | 0.0025 |
| psi | 0.36259434 |
| kgf/cm² | 0.025492905 |
Length & Dimension Converter
Convert millimeters, centimeters, meters, inches and feet.
1 inch = 25.4 mm exactly. 1 international foot = 304.8 mm exactly.
For fractional inches, enter a value such as 1/2 or 12 1/2 and select inches. DN and NPS are nominal pipe sizes, not directly interchangeable measured diameters.
Results rounded to eight significant digits. For reference only — verify before use.
| Unit | Value |
|---|---|
| mm | 324 |
| cm | 32.4 |
| m | 0.324 |
| inches (in) | 12.755906 |
| feet (ft) | 1.0629921 |
Dust Collector Airflow: A Preliminary Estimate
Practical calculations for ducts, enclosing openings and multiple workstations.
How much airflow does my dust collector need? Start with the sources that must be captured, not just the size of the workshop. Check the machine supplier’s extraction requirement first. Where no requirement is available, document the source, hood geometry and operating conditions before estimating.
2 · Estimate each branch
Use specified extraction airflow where available. The tools below check duct flow or an enclosing opening once a suitable velocity is known. They do not select that velocity for you.
3 · Check the whole system
Sum simultaneous branches, then check pressure losses, filter loading, make-up air and dust hazards. A fan must deliver the required airflow at the system’s operating pressure.
Airflow from a Round Duct
Use an actual internal diameter and a measured or independently selected mean duct velocity.
Q = 3,600 × (πD² / 4) × v; D in meters.
Duct velocity is not capture velocity at the dust source. A duct diameter alone cannot establish the airflow required by a process. The example velocity is illustrative, not a recommendation for your dust.
Worked example: 160 mm at 15 m/s → approximately 1,086 m³/h.
Airflow through an Enclosure Opening
For a substantially enclosed source with a defined inward-flow opening.
Q = 3,600 × W × H × v. Sum all openings if more than one admits air.
Use a velocity specified for the process or established by a competent ventilation designer. This is not a remote capture-hood formula. Cross-drafts, source momentum, heat and access openings can change the requirement.
Worked example: 1.0 × 0.8 m opening at an assumed 0.5 m/s → 1,440 m³/h; illustrative only.
Simultaneous Workstation Airflow
Add the required extraction flows for up to three groups of identical stations. Enter zero for unused groups.
Qtotal = Q₁n₁ + Q₂n₂ + Q₃n₃.
Use manufacturer or design requirements for each station. Only exclude idle branches when reliable isolation/control is provided. This total excludes leakage allowances and does not determine fan pressure, branch balancing or minimum duct transport velocity.
Worked example: 3 stations × 1,000 m³/h + 2 stations × 1,500 m³/h → 6,000 m³/h.
Round Duct Diameter from Airflow
Estimate the mathematical diameter for a known airflow and selected transport velocity.
D = 1,000 × √[4Q / (3,600πv)] mm.
Use the result as a dimensional starting point. Select a practical duct size and recheck actual velocity and pressure loss. A larger diameter reduces velocity; it is not automatically better for dust transport.
Worked example: 5,000 m³/h at an assumed 18 m/s → approximately 313 mm.
Do not size dust capture from air changes alone. Q = room volume × air changes per hour describes general ventilation. It does not establish capture at a welding point, grinder or powder release. Confirm capture performance and measured airflow when commissioning. Toxic or combustible dust requires a process-specific assessment.
Design guidance: OSHA Industrial Ventilation Technical Manual · HSE HSG258: Local Exhaust Ventilation. The tools illustrate physical relationships; these references do not certify this calculator or provide one universal design velocity.
HVAC, Heat & Energy Calculators
Thermal power, energy, temperature and the sensible load of an air stream.
Heating & Cooling Capacity Converter
Convert thermal power, such as a heater or cooling coil rating.
1 kW ≈ 3,412.142 BTU/h (IT); 1 US TR = 12,000 BTU/h (IT).
Thermal capacity is not electrical input power. Equipment COP or efficiency is needed to relate the two. Kilocalorie units here use the International Table (IT) definition.
Worked example: 10 kW ≈ 34,121 BTU/h ≈ 2.8435 US TR.
Thermal Energy Converter
Convert an amount of energy, not a heating or cooling rate.
1 kWh = 3.6 MJ = 3,600 kJ. Energy = power × operating time.
Do not compare kWh directly with kW or BTU/h. A power rating needs an operating duration to become an energy quantity.
Worked example: 10 kW sustained for 10 hours = 100 kWh = 360 MJ.
Airflow & Temperature: Sensible Heat Load
Estimate heating or cooling of an air stream for a stated temperature change.
P = ρ × cp × Q × |ΔT| / 3,600 kW; E = P × hours kWh.
Defaults approximate near-room-temperature air. Use density appropriate to the actual airflow conditions. Excludes moisture/latent load, heat recovery, building loads and fan heat. This is thermal demand, not electricity use or guaranteed savings.
Worked example: 10,000 m³/h × 20 K at ρ = 1.2 and cp = 1.005 → 67 kW; over 2,000 hours → 134,000 kWh thermal.
Temperature Converter
Convert a temperature reading between Celsius, Fahrenheit and kelvin.
°F = °C × 9/5 + 32; K = °C + 273.15.
For a temperature difference, 1 K = 1 °C = 1.8 °F of difference. Do not add 32 when converting a temperature difference for the heat-load formula.
Worked example: 20 °C = 68 °F = 293.15 K; a 20 °C difference equals a 36 °F difference.
A Practical Guide to Dust Collection Units
Understand the quantity before converting the number.
CFM and CMH measure airflow
CFM means cubic feet per minute. CMH means cubic meters per hour (m³/h). For the same air conditions, multiply CFM by 1.69901079552 to obtain m³/h. For example, 1,000 CFM is approximately 1,699.0108 m³/h.
Pressure is not airflow
Pa, kPa and inches of water describe pressure. CFM and m³/h describe volume flow. There is no universal Pa-to-CFM conversion: a fan curve, system resistance or a suitable measurement relationship is needed.
SCFM, ACFM and Nm³/h need conditions
Standard or normal flow refers to specified reference conditions, while actual flow refers to operating conditions. A simple unit factor cannot account for temperature, absolute pressure or humidity. Confirm the reference conditions before comparing quotations.
Water-column units need a convention
This tool uses conventional water-column factors. A gauge or specification may use water at a stated temperature instead. Small differences between conversion tools can therefore reflect different definitions rather than a calculation error.
Keep the pressure reference unchanged
Changing Pa to psi does not turn gauge pressure into absolute pressure. A negative gauge reading stays negative after unit conversion. Likewise, static pressure and total pressure are different quantities, not different units.
Use measured dimensions for filter matching
Convert the actual diameter and length, then check mounting details, end caps and seals. For example, 324 mm is approximately 12.755906 inches. Nominal pipe labels such as DN100 or NPS 4 are not substitutes for measured dimensions.
Conversion reference: NIST Guide to the SI — conversion factors by quantity. Airflow factors use the international foot. The inch-of-water value follows the conventional factor listed by NIST. The unit converters and preliminary estimates do not replace complete dust collection system design or performance verification.
Frequently Asked Questions
Quick answers for specification checks and daily engineering work.
Can I size a dust collector from workshop floor area alone?
No. Start with the extraction needs of each dust source and the branches operating together. Hood design, duct transport, pressure losses and dust characteristics also matter. Room air-change calculations do not establish local dust capture.
Does the airflow estimate select a fan or filter size?
No. It is a preliminary flow estimate. Fan selection also needs operating pressure and a fan curve; filter selection needs suitable media, filtration velocity, dust loading and cleaning requirements.
Is the sensible heat result an electricity-saving estimate?
No. The result is thermal load. Electrical use depends on equipment efficiency or COP, operating conditions and other loads. Moisture-related cooling is excluded.
How do I convert CFM to m³/h?
Multiply CFM by 1.69901079552. To convert m³/h to CFM, divide by the same factor. These conversions assume the same air reference conditions.
How many pascals are in one inch of water?
For the conventional inch of water used here, 1 inH₂O is approximately 249.0889 Pa. Check the water-temperature convention when matching a specific instrument or standard.
Is 0.4 MPa the same as 4 bar?
Yes. 0.4 MPa equals 400 kPa, 400,000 Pa and 4 bar. Preserve the original gauge, absolute or differential pressure reference.
Can I convert inches to millimeters using a fraction?
Yes. Choose inches and enter a decimal such as 12.5, a fraction such as 1/2, or a mixed fraction such as 12 1/2. One inch equals exactly 25.4 mm.
Can I save or share a calculation?
Use Copy calculation link to save the selected tool, value and units in the link. Anyone with that link can see those values, so share it only when appropriate. No account is required.
Are the converters free?
Yes. 7US provides these tools as a free resource for the engineering community. No registration, payment or contact details are required.
Put Your Converted Values to Work
Continue with a related tool or discuss the equipment behind the numbers.
Air Recirculation Thermal Estimate →
Explore the sensible heating or cooling load associated with returning filtered workshop air.
Dust Collector Filter Cartridges →
Compare cartridge styles and dimensions when specifying replacement filters.
HEPA Dust Collectors →
Explore cartridge, flat baghouse and wet dust collectors with integrated HEPA final filtration.
Need Help Selecting a Dust Collection System?
Send your converted airflow, pressure requirements, dust characteristics and process details. Our team can review the equipment configuration for your project.
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