Instrumentation calculators that get the numbers right

Free online calculators for process and instrumentation engineers: 4–20 mA scaling, RTD & thermocouple conversion, pressure, flow, level, control valves and calibration — no signup, no fluff.

4 mA 0% 8 mA 25% 12 mA 50% 16 mA 75% 20 mA 100%

    Calculators

    Signal & Loop

    4-20 mA to Process Variable (PV) Calculator

    Convert loop current to process value, percentage and back — with any range.
    Signal & Loop

    mA to Percentage Converter

    Instant 4-20 mA ↔ 0-100 % conversion.
    Signal & Loop

    Current Loop Voltage Drop Calculator

    Will your transmitter power up? Check supply voltage vs loop resistance.
    Signal & Loop

    5-Point Calibration Table Generator

    Generate 0-25-50-75-100 % test points in mA and engineering units.
    Signal & Loop

    Square Root Extraction Calculator (DP ↔ Flow)

    Convert DP signal to flow percentage and mA — the √ law done right.
    Pressure

    Pressure Unit Converter

    bar, psi, kPa, kg/cm², mmH2O, inH2O, mmHg, Torr, atm — all at once.
    Pressure

    Hydrostatic Pressure / Liquid Head Calculator

    Pressure from liquid height and density (and back).
    Pressure

    Gauge ↔ Absolute Pressure Converter

    psig to psia, barg to bara — with altitude-corrected atmospheric pressure.
    Temperature

    PT100 / PT1000 Resistance ↔ Temperature CalculatorSOON

    Callendar–Van Dusen conversion both ways, Class A/B tolerance included.

    Temperature

    Thermocouple mV ↔ Temperature CalculatorSOON

    Types K, J, T, E, N, R, S, B with cold junction compensation.

    Level & Tank

    DP Transmitter Level Calculation — Open TankSOON

    Range, LRV/URV and mA output for open-tank DP level.

    Flow

    Flow Unit ConverterSOON

    m³/h, L/min, GPM, BBL/d, kg/h, Nm³/h, SCFM in one place.

    Control Valves

    Control Valve Cv Sizing — LiquidSOON

    Required Cv from flow, ΔP and specific gravity.

    Browse by category

    Signal & Loop

    4-20 mA scaling, loop power, calibration points and signal conversion.

    Temperature

    RTD and thermocouple conversion, tolerances and temperature units.

    Pressure

    Pressure unit conversion, hydrostatic head and DP level calculations.

    Flow

    Flow unit conversion, DP-to-flow, orifice sizing and gas flow correction.

    Level & Tank

    Tank volume, level-to-volume and level instrument calculations.

    Control Valves

    Cv / Kv sizing and control valve calculations.

    Electrical

    Cable sizing, voltage drop, power and loop wiring calculations.

    Process & General

    PID tuning, unit conversions and fluid properties.

    Calibration

    Errors, uncertainty, test points and calibration scheduling.

    Analyzers

    pH, conductivity, and gas concentration conversions.

    Why ZeroAndSpan?

    Every calculator here is written and verified by an instrumentation engineer — formulas follow the standards (IEC 60751, ISA, NAMUR) and each tool explains its math with a worked example, so you can check the result instead of trusting a black box. Zero and span: the two adjustments every instrument needs, and the two things this site promises to get right.