Engineering calculators that show their working.
31 free tools for the work calibration, metrology and cold-chain teams do every week. Each one states the formula or clause it follows, and all but two run entirely in your browser — the equipment selector and the laboratory finder send what you enter to our server, and say so on their own pages.
Calculators
Type A uncertainty from repeated readings
Paste a column of repeated measurements and get n, the mean, the sample standard deviation, the standard uncertainty of the mean and the degrees of freedom — laid out in the fields the uncertainty budget calculator asks for, including the ν that most budgets quietly drop.
Open calculatorEn number calculator for proficiency testing
Work out En from your result, the assigned value and both expanded uncertainties, with the z-score and z′ where the scheme states a standard deviation for proficiency assessment. It also shows how much of a pass was bought by the uncertainty you claimed.
Open calculatorIQ OQ PQ protocol builder
Build a draft IQ, OQ and PQ protocol for a cold room, chamber, autoclave or vehicle — document control, the test list that suits that equipment, record tables and approval blocks. It will not write your acceptance criteria, and says so.
Open calculatorTemperature mapping data analyser
Paste the export from a finished mapping study and get the gradient, the hot and cold spots, MKT and per-sensor statistics — plus the data-quality checks that catch a channel which quietly stopped reporting on day two.
Open calculatorCalibration interval calculator from as-found history
Paste an instrument's as-found history and see how fast it is actually drifting, how much of its tolerance that consumes, and how long the evidence supports trusting it. The strongest input to an interval is the instrument's own record — this reads it.
Open calculatorThermal mass and thermal lag simulator
Your cold room alarmed at 3 a.m. and the air was above 8 °C for twenty minutes. Whether the product ever got there depends on its thermal mass — work out the time constant for your load and see how much of that excursion it actually followed.
Open calculator3D temperature mapping placement planner
Lay out logger positions in a room, see the layout in three dimensions before you climb a ladder, and export the position table for the protocol. It shows you the gaps in a grid — it does not tell you how many loggers to use, and it explains why not.
Open calculatorTest uncertainty ratio calculator (TUR and TAR)
Work out whether a laboratory's uncertainty is good enough for your tolerance, on the 4:1 basis ANSI/NCSL Z540.3 uses — and see why a healthy TAR can hide a failing TUR.
Open calculatorStandard curve and calibration curve calculator
Paste your reference and indication pairs — a calibration curve or a standard curve, the fit is the same — and get the least-squares line, the residual plot that decides whether to believe it, and the residual standard deviation your uncertainty budget needs.
Open calculatorMeasurement uncertainty budget calculator
Combine Type A and Type B components per the GUM: divisors by distribution, sensitivity coefficients, u_c, effective degrees of freedom and U at k = 2.
Open calculatorGuard band and decision rule calculator
Turn a tolerance and an expanded uncertainty into acceptance limits under ILAC-G8 rules, and see the false-accept and false-reject risks.
Open calculatorMean kinetic temperature (MKT) and excursion assessor
Paste logger readings from storage or a cargo shipment: MKT per ICH Q1A(R2), time out of range, and which figure actually governs the excursion.
Open calculatorPt100 resistance ↔ temperature calculator (IEC 60751)
Convert between resistance and temperature for Pt100 / Pt1000 sensors, with class AA, A, B and C tolerances at that temperature.
Open calculatorDew point and relative humidity calculator
Convert between temperature, relative humidity and dew point, and see how much a temperature error shifts an RH reading.
Open calculatorLogger sampling interval simulator
See what a logger actually records from the same 24 hours at 1, 5, 15, 30 or 60 minute intervals, and watch a real excursion disappear.
Open calculatorThermocouple millivolt to temperature calculator
Convert between millivolts and temperature for type K, T, J, N and E using the NIST ITS-90 reference functions, with proper cold-junction compensation and IEC 60584-1 tolerance classes.
Open calculatorCalibration equipment selector
State the range, the uncertainty you need and what you are calibrating. See which class of equipment fits, from dry block to liquid bath, chamber, furnace or blackbody, with the criterion behind every verdict.
Open calculatorCalibration certificate checker (ISO/IEC 17025 clause 7.8)
Paste the text of a calibration certificate and screen it against ISO/IEC 17025:2017 clause 7.8: uncertainty with k, traceability, as-found and as-left, the decision rule behind a pass, and every other required element, with the matched text shown for each.
Open calculatorAccredited calibration laboratory finder
State the range, the uncertainty you need and what you are sending for calibration. See which accredited laboratories cover it, with the CMC and accreditation number behind every match.
Open calculatorTemperature converter: °C, °F, K and °R, points and intervals
Convert a temperature between Celsius, Fahrenheit, kelvin and Rankine, and convert a temperature difference or uncertainty separately, because the two do not follow the same rule.
Open calculatorPressure unit converter with gauge and absolute
Convert between Pa, kPa, MPa, bar, mbar, psi, atm, mmHg, Torr, inHg, water columns and kgf/cm², and move between gauge and absolute pressure with the local atmosphere.
Open calculator4–20 mA current loop calculator
Scale a 4–20 mA signal to engineering units and back, see where it falls against the NAMUR NE 43 fault thresholds, and get the five-point calibration table for your range.
Open calculatorInstrument accuracy calculator: % of reading, % of full scale and counts
Turn a datasheet accuracy such as ±(0.1 % of reading + 0.05 % of full scale + 2 counts) into the absolute error at your reading, and see how it grows as the reading falls.
Open calculatorNTC thermistor calculator: beta and Steinhart–Hart
Convert an NTC thermistor's resistance to temperature and back with the beta equation, or fit Steinhart–Hart coefficients to three calibration points and use those.
Open calculatorRelative humidity from wet-bulb and dry-bulb temperature
Enter the dry- and wet-bulb readings from a psychrometer and the station pressure to get relative humidity, dew point and vapour pressure, with the psychrometer coefficient shown.
Open calculatorBalance minimum weight calculator (USP <41> and <1251>)
Paste ten or more replicate weighings, or enter a standard deviation, and get the smallest net weight your balance can weigh to 0.10 % accuracy, with the USP readability floor applied.
Open calculatorpH electrode slope and offset calculator
Enter the millivolt readings your pH electrode gives in two or three buffers and get the slope as a percentage of the ideal Nernst value, the offset at pH 7, and a check against your own limits.
Open calculatorPt100 lead wire error calculator: 2-wire, 3-wire and 4-wire
See how many degrees your Pt100 or Pt1000 cable adds to the reading in a 2-, 3- or 4-wire circuit, and how long a 2-wire run can be before the error passes a limit you choose.
Open calculatorPressure gauge calibration calculator: error, hysteresis and head correction
Paste the reference and gauge readings from a calibration run and get each point's error, the hysteresis between the rising and falling series, and the head correction people forget.
Open calculatorCalibration worksheet: error, TUR and a decision at every point
Paste the readings from a calibration and get the error at each point, the test uncertainty ratio, and a pass, conditional pass, conditional fail or fail under the guard band you choose — as found and as left — with a draft record to copy.
Open calculatorIQ OQ PQ execution workspace: record results and deviations
Run a qualification, not just write it. Record each IQ, OQ and PQ test's result against your own acceptance criterion, raise and close deviations, see what stops a stage closing, and export a summary. Your work is kept in this browser.
Open calculatorPlatform
AI technical assistant
Evidence-cited answers with deterministic uncertainty calculations and a validation status.
Open the assistantTemperature mapping analyzer
Upload CSV/XLSX, run pre-flight and data-quality checks, get statistics, hot/cold spots, excursions and a draft report.
See the workflowCalibration workflow
Request to certificate with the same uncertainty, drift and decision-rule functions, plus technical review and records.
See what is plannedThe guides behind the arithmetic
Each calculator does one step of a longer job. These explain the rest of it — where the numbers come from, which standard fixes them, and what the result does and does not license you to say.
- UncertaintyBuilding an uncertainty budget step by step
- MetrologyRectangular, triangular and normal distributions in uncertainty budgets
- MetrologyType A vs Type B uncertainty: the difference that matters
- UncertaintyEffective degrees of freedom and when k = 2 is not enough
- UncertaintyUncertainty budget for a thermocouple calibration
- GDP / GMPMean kinetic temperature (MKT): what it is and when to use it
- EquipmentPt100 tolerance classes explained (IEC 60751)
- EquipmentThermocouple types and tolerance classes (IEC 60584)
- CalibrationSelecting a reference thermometer
- CalibrationSelf-heating in resistance thermometers
- CalibrationCalibrating relative-humidity sensors
- CalibrationHow thermocouples are calibrated
- Temperature MappingChoosing sampling interval and study duration
- CalibrationLiquid bath versus dry-block calibrator
- GDP / GMPHandling temperature excursions in storage and distribution
The calculators implement the published formulas (GUM, ILAC-G8, ICH Q1A, IEC 60751, Magnus) and are covered by automated tests against reference values. They are aids to a competent person, not a substitute for a documented method or a reviewer.