Free tools for PLC • SCADA • EtherCAT • CODESYS • OT

Controls engineering calculations. Answers in seconds.

Size historian storage, check PLC task timing, plan Modbus and EtherCAT networks, estimate cabinet cooling, and size 24VDC power—right in your browser.

No account. No spreadsheet. No black box—assumptions are shown with every calculator.

✓ 9 free calculators✓ Instant results✓ Mobile-friendly✓ Assumptions shown

9 free controls calculators

Choose the engineering problem you need to solve. Each tool gives an immediate result and shows the assumptions behind the calculation.

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Historian Storage

Estimate SCADA historian data volume and a practical SSD size.

Calculation assumptions

Planning estimate uses 100 bytes per recorded tag change, then adds your selected headroom plus OS/application reserve. Real storage varies with historian schema, compression, deadband, indexing, and database overhead.

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Enclosure Cooling

Estimate sealed-cabinet temperature rise and cooling required.

Calculation assumptions

Uses ΔT ≈ P/(h×A) with h = 5.5 W/m²·K and an exposure factor applied to enclosure surface area. Fan airflow is a planning estimate. Solar gain, internal hot spots, filters, altitude, and certified enclosure data are not modeled.

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Modbus RTU Timing

Estimate polling-cycle time, refresh rate, and a practical response timeout.

Calculation assumptions

Models a typical 8-byte read request and a response of 5 + 2×registers bytes. For ≤19,200 baud, t3.5 is 3.5 character times; above 19,200 baud, 1.75 ms is used. Device processing delay is entered separately.

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24VDC Power Supply

Add common panel loads and size a practical DIN-rail power supply.

Calculation assumptions

Sums entered DC loads and applies your design headroom. Recommended standard wattage is rounded up to a common DIN-rail size. Verify startup/inrush current, redundancy, ambient derating, NEC/UL requirements, and manufacturer curves separately.

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CODESYS Task & Jitter

Turn CODESYS task-monitoring values into utilization, timing margin, and jitter indicators.

Calculation assumptions

Uses the task interval and observed CODESYS monitoring values you enter. Utilization is execution time ÷ task interval; peak-to-peak jitter is maximum jitter minus minimum jitter. The health message is a planning indicator only and does not certify real-time performance.

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EtherCAT Cycle Time

Estimate the communication and application timing budget for a target EtherCAT cycle.

Calculation assumptions

First-pass model: frame time ≈ 5 µs overhead + 0.08 µs per process-data byte at 100 Mbit/s, plus your entered slave delay, cable propagation at about 0.005 µs/m, application execution, and jitter reserve. Actual masters, frame layouts, slave types, OS/runtime behavior, and minimum device cycle times can change the result.

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EtherCAT PDO Size

Add common EtherCAT device groups and estimate total cyclic RxPDO and TxPDO data.

Calculation assumptions

Groups devices for quick planning and treats the entered bytes as total cyclic RxPDO + TxPDO payload per device. The RxPDO percentage splits that payload directionally. Serialization shows payload-only wire time at 100 Mbit/s and excludes Ethernet/EtherCAT framing and slave propagation.

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EtherCAT Distributed Clock Checker

Check the basic relationship between the master cycle, Sync0 factor, shift, and slave minimum cycle.

Calculation assumptions

Checks arithmetic consistency only: Sync0 cycle = master cycle × factor, the selected cycle is compared with the entered slave minimum, and shift is checked against the calculated Sync0 period. Always use the slave ESI/device documentation and the master vendor's DC guidance for final settings.

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4–20 mA Analog Scaling

Convert a loop current to its engineering value — or a value back to mA — for any transmitter range.

Calculation assumptions

Linear 4–20 mA scaling only. Below 4 and above 20 mA the formula extrapolates outside the calibrated range — treat those readings as process, calibration, or wiring problems, not process values. Square-root or other transmitter curves are not modeled.

Controls Toolkit preview

Take the next design step in Excel or PDF.

Get all 12 Toolkit resources — IPC sizing, EtherCAT timing, power, historian, networking, RFQ, and commissioning templates — with sample data, formulas, printable worksheets, and engineering checks already built in.

Included now

  • Industrial PC sizing and EtherCAT timing-budget worksheets
  • 24 VDC power, historian storage, and Ethernet bandwidth planning
  • CODESYS, Modbus, and FAT/SAT commissioning logs and worksheets
  • OT architecture review, RFQ template, sample project, and quick-reference sheets

Free access by email signup. Download editable Excel and Word editions plus printable PDFs.

Built for controls engineers—not generic calculator traffic.

ControlsCalculator.com is built for automation, SCADA, PLC, OT, and industrial-computing professionals who need a fast engineering estimate without opening a spreadsheet or creating an account.

More about the site and the engineer behind it →

What this site is for

  • Early design and product sizing
  • Commissioning sanity checks
  • Comparing architecture options
  • Quick calculations from a phone or laptop

These calculators are planning aids, not substitutes for manufacturer data, applicable codes, certified testing, or a professional engineering review.

Frequently asked questions

Are these calculators free?

Yes. The calculators are intended to be usable immediately without an account, login, or subscription.

Do you save my calculation data?

No. In this version, calculations run in your browser and the site does not send calculator inputs to a server.

Are the results suitable for final engineering sign-off?

No. They are planning and sanity-check tools. Final designs should be verified against equipment datasheets, applicable standards, site conditions, and qualified engineering judgment.

Why does the historian calculator use 100 bytes per tag change?

It is a practical planning assumption for an uncompressed tag-change record. Actual historian storage depends on database implementation, compression, deadband, indexing, metadata, and logging behavior.

Does the Modbus calculator guarantee a polling rate?

No. It estimates wire time plus the device-response delay you enter. Real systems can be slower because of gateway latency, retries, serial adapters, OS scheduling, and slave processing time.

What does the CODESYS task analyzer tell me?

It converts the task interval, execution-time, watchdog, and jitter values you enter into utilization and timing-margin indicators. It is intended for troubleshooting and planning, not as a real-time certification.

Does the EtherCAT cycle calculator guarantee a cycle time?

No. It estimates a first-pass timing budget from process-data size, slave/cable propagation, application execution, and jitter reserve. Real performance depends on the EtherCAT master, operating system/runtime, frame layout, slave characteristics, and device-specific minimum cycle times.

Can I request another OT calculator?

Yes. Use the request form below to suggest a calculator, flag an engineering assumption, request a feature, or ask for an engineering review. Your submission is sent to info@forwardsystemlabs.com.

Need help with an industrial controls application?

Describe your PLC, SCADA, EtherCAT, industrial PC, networking, or sizing requirement. We will review the information and respond by email.

Please do not include passwords, confidential credentials, or export-controlled information.
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