Six free calculators for the numbers instrumentation engineers work out every day: pressure and flow unit conversion, turndown ratio, DP level calibration, mag meter velocity and 4–20 mA scaling. Type a value and the result updates instantly. No sign-up, nothing to download.
Free · No sign-up · Results update as you type · Metric and imperial units
| Unit | Equivalent value |
|---|
Need the instrument? Pressure transmitters → Pressure transducers → Pressure gauges →
Show reference formula
value_Pa = value × factor[from_unit]
result_unit = value_Pa ÷ factor[result_unit]
e.g. 1 bar = 100 000 Pa · 1 psi = 6 894.757 Pa · 1 atm = 101 325 Pa
| Unit | / second | / minute | / hour | / day |
|---|
The highlighted cell matches what you entered above. Every other cell is that same flow rate re-expressed in a different unit/time combination — e.g. read the bbl row's / day column for oil bbl/day, or the MMSCF row's / day column for MMSCFD.
Need the instrument? Flow meters → Electromagnetic flow meters → Flow computers →
Show reference formula
value_base/s = value × unit_factor ÷ time_seconds
result_cell = value_base/s ÷ unit_factor[row] × time_seconds[column]
MMSCF uses standard conditions (60°F, 14.696 psia). Converting between volumetric and mass flow requires fluid density — not included here.
Need the instrument? Vortex flow meters → Ultrasonic flow meters → Thermal mass flow meters →
Show reference formula
Higher ratio → instrument holds accuracy over a wider range.
SG1 process fluid · L span between taps · h transmitter offset below lower tap. The upper side is open to atmosphere, so only one process connection is needed.
SG1 process fluid · L span between taps · h transmitter offset below lower tap. The dry leg carries vapor pressure only — its length adds no column weight, so vapor pressure cancels out of the DP.
SG1 process fluid · SG2 wet-leg fill fluid · L span between taps · h transmitter offset below lower tap · H wet leg height, transmitter to upper tap. HP = process (dry, short leg) · LP = reference (wet, filled leg).
Go deeper: DP level calculation guide → Need the instrument? Level transmitters → Pressure transmitters →
Show reference formula
Need the instrument? Electromagnetic flow meters → All flow meters →
Show reference formula
Flow rate: Q = V × A
Velocity: V = Q ÷ A
Electromagnetic flow meters typically need 0.3–10 m/s line velocity for a reliable, low-noise signal — outside that band, accuracy and repeatability degrade even though the meter still reads.
Need the instrument? Signal conditioners → Signal isolators → Process indicators →
Show reference formula
Signal = Signal_lo + % × (Signal_hi − Signal_lo)
(Signal → PV runs the same equations in reverse.)
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Worked examples
See how each calculator works
Pressure Unit Converter
A transmitter is ranged 0–10 bar. Enter 10 bar and read 1,000 kPa, 145.04 psi or 10.197 kgf/cm².
Formula: value in Pa = value × unit factor, then divide by the target unit’s factor.
Flow Unit Converter
A pump is rated 50 m³/h. Pick m³ and per hour, enter 50, and read 833.3 L/min, 13.89 L/s or 220.1 US gpm.
Formula: choose the volume or mass unit and the time unit separately; every combination is shown at once.
Turndown Ratio Calculator
A flow meter reads from 8 m³/h up to 100 m³/h. Turndown = 100 ÷ 8 = 12.5 : 1, so the lowest usable flow is 8% of the maximum.
Formula: turndown ratio = maximum flow ÷ minimum flow.
DP Level Calculator
Closed tank with a wet leg: SG 1.0, taps 2.0 m apart, transmitter 0.5 m below the lower tap, 2.5 m wet leg of SG 1.0. The calibration is LRV −19.61 kPa, URV 0 kPa.
Formula: LRV = g·(SG1·h − SG2·H), URV = g·(SG1·(h + L) − SG2·H). Full method in our DP level calculation guide.
Velocity ↔ Flow (Mag Meter)
A DN100 line (100 mm bore) running at 2 m/s carries about 56.5 m³/h. Enter the flow instead to see the velocity.
Formula: Q = V × A, where A = π ÷ 4 × D².
PV ↔ mA Converter
A 0–10 bar transmitter on 4–20 mA gives 12 mA at 5 bar. Reading 8 mA means (8 − 4) ÷ 16 × 10 = 2.5 bar.
Formula: mA = 4 + (PV − LRV) ÷ (URV − LRV) × 16.
FAQ
Common questions
How do I convert 4–20 mA to a process value?
Subtract 4 from the current, divide by 16, then multiply by the span and add the lower range value: PV = LRV + (mA − 4) ÷ 16 × (URV − LRV). For a 0–10 bar transmitter reading 12 mA, that is 5 bar.
Why does a 4–20 mA loop start at 4 mA instead of 0?
The 4 mA “live zero” separates a real 0% reading from a broken wire or a dead loop, and it leaves enough current to power a two-wire transmitter. NAMUR NE43 uses signals at or below 3.6 mA and at or above 21 mA to flag a fault.
What is turndown ratio and why does it matter?
Turndown ratio is the maximum flow divided by the minimum flow a meter or control valve can handle within its stated accuracy. A 10 : 1 meter on a 200 m³/h line holds accuracy down to 20 m³/h. Make sure your normal operating flow sits comfortably inside that range, not at its edge.
When should I use a wet leg for DP level measurement?
Use a wet (filled) reference leg when vapour above the liquid can condense, such as steam or humid services, because condensate in a dry leg adds an unpredictable head. A wet leg gives a constant reference pressure but shifts the calibration to a negative LRV, so confirm the transmitter supports zero elevation.
What velocity range does an electromagnetic flow meter need?
Most electromagnetic flow meters are specified from roughly 0.3 m/s up to 10 m/s, with the best performance in the middle of that band. They also need a conductive liquid and a full pipe, so always check the datasheet for the exact limits.
How accurate are these calculators?
They use standard conversion factors and textbook formulas, so they suit estimating, sizing and sanity checks. For calibration and safety-critical work, confirm every value against the instrument datasheet and your plant procedures.
