Free interactive calculators, quick-reference charts, and curated resources for instrumentation technicians and electrical professionals. Built for the field — fast, accurate, mobile-ready.
Every calculator runs instantly in your browser — no app, no account, no loading spinner. Designed for a phone screen in the field.
The most complete 4–20 mA reference tool online. Five calculators in one widget — everything from basic signal conversion to full printable calibration tables.
Searchable, printable tables built for the bench and the field. Updated to current ISA, IEC, and NEC standards.
| % Span | mA Signal | V / 250 Ω | V / 500 Ω | PSI Value |
|---|---|---|---|---|
| 0% | 4.000 mA | 1.000 V | 2.000 V | 0.000 PSI |
| 10% | 5.600 mA | 1.400 V | 2.800 V | 10.000 PSI |
| 25% | 8.000 mA | 2.000 V | 4.000 V | 25.000 PSI |
| 50% | 12.000 mA | 3.000 V | 6.000 V | 50.000 PSI |
| 75% | 16.000 mA | 4.000 V | 8.000 V | 75.000 PSI |
| 90% | 18.400 mA | 4.600 V | 9.200 V | 90.000 PSI |
| 100% | 20.000 mA | 5.000 V | 10.000 V | 100.000 PSI |
InstruTools was built out of a simple frustration: too many useful reference tools scattered across outdated PDFs, manufacturer websites that require logins, and phone apps that don't work without cell service.
Everything here is free, runs in your browser, works on your phone, and doesn't require an account. Bookmark it. Use it on the job.
All formulas reference ISA, IEC, and NEC standards. If you spot an error or want a calculator added, use the request form.
Vetted links to official standards bodies, manufacturer libraries, and trusted industry sources — all open in new tabs.
All tools are free, no account needed, and optimized for your phone or tablet on the job site.