Vibration Severity Checker (ISO 10816) Skip to main content
Shops & Outbuildings Free Pro Features Available

Vibration Severity Checker - ISO 10816 / 20816 Zone Classification for Rotating Equipment

Classify machine vibration levels against ISO 10816 & ISO 20816 standards for pumps, motors, fans, compressors & turbines

Check vibration severity for rotating machinery against the widely used legacy ISO 10816-1 classification zones. Enter vibration velocity in mm/s or in/s (RMS, peak, or peak-to-peak with a disclosed sinusoidal conversion) and select the machine class (Class I-IV by power and foundation) to get a severity screen from Zone A (new machine condition) through Zone D (damage may be occurring). Includes the Class I-IV zone boundary reference table, a common fault-frequency diagnostic prompt, and measurement guidelines. ISO 10816-1 has been replaced by the ISO 20816 series; treat zone results as a screening guideline, not an acceptance limit, alarm/trip setpoint, reliability verdict, or operating decision.

Pro Tip: Overall vibration level tells you severity, but frequency analysis tells you the cause. A machine at 0.3 in/s peak could have imbalance (1× RPM), misalignment (2× RPM), bearing defects (BPFO/BPFI), or looseness (sub-harmonics). Always pair severity checks with spectrum analysis. If overall vibration doubles, you have already lost 75% of remaining bearing life - do not wait for the next scheduled outage to investigate.

Check coupling alignment as a vibration root cause

Coupling Alignment Calculator →

Review bearing relubrication intervals

Lube Interval Calculator →

Estimate remaining bearing life

Bearing Life Calculator →

Read the vibration analysis basics guide

Vibration Analysis Basics →

PREVIEW All Pro features are currently free for a limited time. No license key required.

Vibration Severity Checker
Pop Out

How It Works

  1. Select Machine Class

    Choose the legacy ISO 10816-1 machine classification: Class I (small machines up to 15 kW), Class II (medium machines 15-75 kW), Class III (large machines over 75 kW on rigid foundations), or Class IV (large machines on flexible foundations). Different classes have different severity thresholds.

  2. Enter Vibration Reading

    Input the overall vibration velocity value from your analyzer or portable meter in mm/s or in/s, and tell the tool whether the reading is RMS, peak, or peak-to-peak. Peak readings are converted to RMS using a disclosed sinusoidal assumption; direct RMS measurement is recommended.

  3. Review Severity Calculator

    See the legacy zone classification: Zone A (new/reconditioned baseline), Zone B (legacy long-term-operation screen), Zone C (investigation prompt), or Zone D (urgent review prompt). Each zone shows the velocity ranges for your machine class.

  4. Reconcile Before Setpoint Decisions

    Zone boundaries are general screening guidelines, not alarm/trip setpoints. Reconcile the result with the applicable current ISO 20816 machine-specific part, manufacturer acceptance limits, and your facility monitoring program before programming setpoints or making operating decisions.

Built For

  • Vibration analysts performing route-based data collection on plant rotating equipment
  • Maintenance planners using severity trends as review prompts before scheduling maintenance work
  • Millwrights screening vibration after motor, pump, or fan installations before OEM or contract acceptance checks
  • Reliability engineers using the zone table as a starting reference before qualified program-specific limit review
  • Plant operators performing daily walk-around vibration checks with handheld meters
  • Commissioning technicians screening readings before formal acceptance against contractual vibration limits

Features & Capabilities

Legacy ISO 10816-1 Zone Calculator

Classifies vibration into Zones A through D using the widely circulated legacy ISO 10816-1 Class I-IV guideline table, covering rigid and flexible foundation classes by power range. The tool discloses that ISO 10816-1 has been withdrawn and replaced by the ISO 20816 series.

Multi-Unit, Multi-Measurement Input

Accepts vibration velocity in mm/s or in/s, entered as RMS, peak, or peak-to-peak. Peak values are converted to RMS via the sinusoidal assumption (peak / sqrt(2)) with an explicit warning that the conversion is unreliable for real broadband machinery vibration.

Source Boundary Disclosure

Every result carries the source boundary: zone values are screening guidelines, not manufacturer acceptance limits, commissioning limits, or alarm/trip setpoints, and the applicable current standard may use a different scheme with different boundaries.

Zone Boundary Reference Table

Shows the full legacy Class I-IV boundary table (mm/s RMS) on screen and in the PDF report so the reading can be compared across classes and re-checked by a reviewer.

Diagnostic Frequency Reference

Quick-reference table of common vibration fault frequencies: 1× RPM (imbalance), 2× RPM (misalignment), bearing defect frequencies (BPFO, BPFI, BSF, FTF), gear mesh, and vane/blade pass frequencies to guide follow-up analysis.

Comparison

ISO Zone Class I (mm/s) Class II (mm/s) Class III (mm/s) Class IV (mm/s) Condition
Zone A 0 - 0.71 0 - 1.12 0 - 1.8 0 - 2.8 New machine baseline
Zone B 0.71 - 1.8 1.12 - 2.8 1.8 - 4.5 2.8 - 7.1 Acceptable long-term
Zone C 1.8 - 4.5 2.8 - 7.1 4.5 - 11.2 7.1 - 18 Investigate / short-term
Zone D > 4.5 > 7.1 > 11.2 > 18 Damage occurring

Assumptions

  • Vibration measurements are taken at the bearing housing in the direction of highest amplitude.
  • Machine is operating at steady-state conditions (not during startup, shutdown, or transients).
  • Measurement instrument is calibrated and has adequate frequency range for the machine speed.
  • Legacy ISO 10816-1 machine class is correctly selected for the equipment type and mounting.
  • Velocity readings are broadband RMS values measured in the 10-1000 Hz frequency range.

Limitations

  • Does not perform spectral analysis or identify specific fault frequencies (bearing, gear mesh, imbalance).
  • Zone thresholds are general guidelines and may not apply to all machine configurations.
  • Low-speed machines (below 120 RPM) may require displacement-based criteria instead of velocity.
  • Does not account for structural resonance, foundation flexibility, or piping strain effects.
  • Cannot replace trained vibration analyst interpretation for root cause diagnosis.

References

  • ISO 10816-1:1995 (withdrawn) - Mechanical Vibration, Evaluation of Machine Vibration by Measurements on Non-Rotating Parts, Part 1 General Guidelines (basis of the legacy Class I-IV zone table).
  • ISO 10816-3 - Mechanical Vibration, Evaluation of Machine Vibration by Measurements on Non-Rotating Parts.
  • ISO 20816-1 - Mechanical Vibration, Measurement and Evaluation of Machine Vibration (general guidelines).
  • ISO 2954 - Mechanical Vibration of Rotating and Reciprocating Machinery, Requirements for Instruments.
  • Vibration Institute Category I-IV analyst training body of knowledge.

Frequently Asked Questions

ISO 10816 is a legacy international standard family for evaluating machine vibration by measurements on non-rotating parts (bearing housings, structural supports). The app carries a widely circulated ISO 10816-1 Class I-IV guideline zone table for broadband velocity screening. ISO 10816-1 has been withdrawn and replaced by the ISO 20816 series, and alarm/trip limits must come from the applicable machine-specific standard, OEM limits, risk policy, and qualified analyst review.
Displacement (mils or micrometers) measures how far the surface moves and is most useful for low-frequency vibration below 600 CPM. Velocity (in/s or mm/s) measures how fast the surface moves and is the standard measurement for general machinery vibration between 600 and 60,000 CPM because it correlates well with vibration severity across a broad frequency range. Acceleration (g) measures force and is best for high-frequency vibration above 60,000 CPM, particularly bearing defects and gear mesh.
The legacy Class II table places 2.8 mm/s RMS at the Zone B/C boundary and 7.1 mm/s RMS at the Zone C/D boundary, but those are screening rows, not a motor acceptance limit. Actual acceptability depends on the motor, driven equipment, bearings, foundation, speed, measurement location, applicable ISO 20816 part, OEM limits, commissioning contract, and qualified vibration analyst review.
Industry best practice is monthly readings for most process-critical rotating equipment. Equipment showing stable Zone A/B vibration can be extended to bi-monthly or quarterly. Any machine in Zone C should be monitored weekly or bi-weekly to track the rate of change. Zone D equipment needs continuous online monitoring or daily manual checks until corrective action is taken. NEMA MG-1 and API 610/541 provide additional guidance for specific equipment types.
Vibration at 1× running speed is predominantly caused by mass imbalance - uneven weight distribution around the axis of rotation. Other 1× causes include bent shafts, eccentric rotors, and thermal bowing. Imbalance produces a sinusoidal vibration at exactly 1× RPM with relatively stable amplitude. If the 1× amplitude changes with temperature, suspect thermal bow. If it changes with load, suspect eccentricity. Field balancing typically reduces 1× vibration by 70-90% in a single correction.
Strong vibration at 2× running speed is the classic signature of shaft misalignment, both angular and offset. Misalignment forces the shaft coupling to flex twice per revolution, producing a dominant 2× component. Other causes of 2× vibration include cracked shafts, stiffness asymmetry, and looseness. When the 2× amplitude exceeds 50% of the 1× amplitude, misalignment is the primary suspect. Verify with coupling alignment measurements using dial indicators or laser alignment tools.
For a sinusoidal vibration signal: mm/s RMS = in/s peak × 25.4 ÷ 1.414 = in/s peak × 17.96. So 0.3 in/s peak equals approximately 5.4 mm/s RMS. Real machine vibration is not purely sinusoidal, so this conversion is approximate. For broadband vibration with multiple frequency components, the actual RMS-to-peak ratio can range from 1.4 to 4.0 or higher. When in doubt, set your analyzer to measure directly in the unit your severity standard uses.
ISO 20816 is the replacement series for ISO 10816. Current use should start with the machine-specific ISO 20816 part and OEM/contract limits, not this legacy Class I-IV table. The app keeps the old table only as a disclosed screening reference because it remains widely circulated in maintenance discussions.
Disclaimer: This tool provides a legacy ISO 10816-1 zone screening reference. Actual acceptable vibration levels depend on machine type, bearing design, foundation, speed, measurement quality, operating conditions, the applicable ISO 20816 part, manufacturer limits, and facility maintenance policy. Vibration analysis requires trained personnel for diagnosis and operating decisions. ToolGrit does not provide predictive maintenance, alarm/trip setpoints, or reliability engineering services.

Learn More

Shops & Outbuildings

Vibration Analysis Basics: ISO 10816, Severity Zones & Machine Classes

Introduction to machine vibration analysis. ISO 10816 severity classification, velocity vs displacement vs acceleration, machine groups, and when to act on vibration readings.

Read Guide →

Related Tools

Shops & Outbuildings Live

Shop Heater BTU Sizing Calculator

Calculate the exact BTU output your shop or garage heater needs. Factors in wall R-values, ceiling insulation, slab edge loss, overhead door infiltration, and air changes per hour to size propane, natural gas, and electric heaters correctly.

Launch Tool →
Shops & Outbuildings Live

Overhead Door Infiltration Loss Calculator

Calculate heat loss through overhead doors in shops, garages, and warehouses. Compares open-door vs closed-door losses, seal condition impact, and annual cost of infiltration with payback on door seals and high-speed doors.

Launch Tool →
Shops & Outbuildings Live

Long-Run Voltage Drop Calculator

Calculate voltage drop for long wire runs to detached shops, barns, garages, and outbuildings. Compares copper vs aluminum, shows motor starting voltage impact, and recommends the right wire size for your distance and load.

Launch Tool →