4-20 mA Calculator

4-20 mA Formula

Worked Example

A 0–10 bar pressure transmitter reading 2.5 bar:

1. I = 4 + 16 × (PV − LRV) ÷ (URV − LRV)
2. I = 4 + 16 × (2.5 − 0) ÷ 10 = 8 mA

Voltage across a 250 Ω resistor: 2 V

GATE tip

Loop voltage budget: the supply must cover the transmitter’s minimum voltage plus 20 mA × (loop resistance). A 24 V supply with a 12 V transmitter allows 600 Ω of loop.

More Sensors and Industrial Instrumentation Calculators

• RTD Calculator

  R = R₀(1 + AT + BT²) for T ≥ 0 °C

  A = 3.9083 × 10⁻³, B = −5.775 × 10⁻⁷; below 0 °C add C(T − 100)T³, C = −4.183 × 10⁻¹²

  Example: A Pt100 at 100 °C: Resistance R = 138.5055 Ω.

  Open the rtd calculator →

• Strain Gauge Calculator

  ΔR/R = GF × ε

  quarter bridge Vₒ ≈ V_ex GF ε / 4; half (bending) V_ex GF ε/2; full V_ex GF ε

  Example: A 350 Ω gauge, GF = 2, at 1000 µε in a quarter bridge with 5 V excitation: Bridge output Vₒᵤₜ = 2.4975 mV.

  Open the strain gauge calculator →

• Thermistor Calculator

  R = R₀ exp[B(1/T − 1/T₀)]

  T in kelvin; inverse 1/T = 1/T₀ + ln(R/R₀)/B

  Example: A 10 kΩ (at 25 °C) NTC thermistor with B = 3950 K at 0 °C: Resistance R = 33.6206 kΩ.

  Open the thermistor calculator →

Frequently asked questions

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.