Engineering Unit Converter: Stress, Force, Length & 40+ Dimensions

Check	IND	US	EU	ISO
Unit conversion	implemented	—	—	—

How engineers convert between unit systems

Mixed units are an everyday hazard. A German mill certificate lists yield in MPa, an American code table uses ksi, and a shop drawing shows inches while the FEA model is in millimetres. One wrong conversion factor can turn a safe design into a failure. A reliable unit converter that enforces dimensional consistency — force cannot become length — eliminates transcription errors and provides a full equivalence table for audit trails.

This guide covers supported dimensions, the conversion model, and common pitfalls with affine scales (temperature) and compound units.

Dimension families and common conversions

Dimension	Example units	Notes
Length	m, mm, in, ft, mil	Most frequent conversion
Force	N, kN, lbf, kgf	Weight vs force confusion
Stress / pressure	Pa, MPa, psi, ksi, bar	Code tables vary by system
Moment / torque	N·m, kN·m, lbf·ft, lbf·in	Beam/shaft design
Area	mm², cm², in², ft²	Section properties
Mass	kg, g, lb, slug	Density and dynamics
Temperature	°C, °F, K, °R	Affine (offset) scales
Energy	J, kJ, BTU, ft·lbf, kWh	Thermal and mechanical
Power	W, kW, hp, BTU/h	Motor and thermal sizing
Velocity	m/s, km/h, ft/s, mph	Flow and dynamics
Density	kg/m³, lb/ft³, g/cm³	Material properties
Flow rate	m³/s, L/min, gpm	Hydraulic and cooling

Engineering workflow

Identify source dimension — what physical quantity is being converted (stress, not force).
Select source and target units — from the dimension's unit registry.
Enter value — numeric magnitude.
Read result — converted value plus full equivalence table for all registered units.
Verify sanity — 1 MPa = 145 psi, 1 inch = 25.4 mm, 1 lbf = 4.448 N.

Key quantities and formulas

Linear conversion model:

Q_{target} = Q_{source} \cdot \frac{k _{source \to base}}{k _{target \to base}}

Affine temperature conversions:

T_{K} = T_{C} + 273.15, T_{F} = 1.8 T_{C} + 32

Compound unit example (stress):

1 MPa = 1 0^{6} Pa = 145.038 psi

Worked example

Given: A vessel design pressure of 150 psi. Convert to MPa and bar for an EN code check.

Select dimension: pressure.
Enter 150 psi.
Result: $150 \times 6.89476 \times 1 0^{- 3} = 1.034$ MPa = 10.34 bar.
Equivalence table also shows 103.4 kPa, 1.021 atm, 10{,}342 mmH₂O.

Common mistakes and checks

Confusing mass (kg) and force (kgf or N) — especially in legacy metric drawings.
Forgetting the offset in temperature — °C to K is additive, not multiplicative.
Using psi for stress when the code table is in ksi (factor of 1000).
Mixing lbf·ft (torque) and ft·lbf (energy) — dimensionally identical, contextually different.
Dropping prefixes — MPa vs Pa is a factor of 10⁶.

FAQ

Can I convert between different dimensions?

No. The converter enforces dimensional consistency — force cannot convert to length. If you need a derived quantity (e.g., stress = force / area), compute it in the appropriate module.

How is precision handled?

Conversion factors use IEEE 754 double precision internally. Display rounding is controlled in the UI — the underlying value retains full precision for downstream calculations.

Are all unit systems supported?

The converter covers SI, US customary, and common engineering units. Obscure or industry-specific units may not be registered. Compound units (e.g., lbf·ft) must use predefined dimension entries.

How does this interact with module unit selectors?

Each PhyCalcPro module has per-field unit selectors backed by the same conversion registry. The standalone converter is for quick lookups; module-level selectors handle conversion at the solver boundary automatically.

Use the PhyCalcPro calculator

Open the Unit converter. Select a physical dimension, enter a value with source unit, and read the converted result plus a full equivalence table for all units in the dimension.

Purpose

Convert numeric values between engineering unit systems across PhyCalcPro dimensions — length, area, mass, force, stress, pressure, moment, torque, energy, power, velocity, flow, density, frequency, time, temperature, and related quantities.

Physics & theory

Physical quantities are expressed as value times unit within a dimension. Conversion normalises to SI base via toBase, then scales to target unit via fromBase. Dimensionality is enforced — force cannot convert to length. Temperature conversions use offset (affine) scales.

Governing equations

Q_{target} = Q_{source} \cdot \frac{k _{source \to base}}{k _{target \to base}}

For affine temperature: $T_{K} = T_{C} + 273.15$ , $T_{F} = 1.8 T_{C} + 32$ .

Numerical method

Registry-based conversion: toBase(value, dimension, fromUnit) then fromBase(base, dimension, toUnit). The UI lists every unit registered for the selected dimension and live-updates a full equivalence table.

Inputs

Parameter	Description
Value	Numeric magnitude
Dimension	Physics dimension key
From unit, to unit	Source and target unit strings

Outputs

Converted value in target unit, echo of unit keys, equivalence table for all units in the dimension.

Design codes & checks

Indicative: Unit conversion (utility tool)

Assumptions & limitations

Conversions within a single dimension only.
Precision follows IEEE double — display rounding handled in UI.
Not every obscure unit is registered.
Currency and mixed dimensionless ratios are not supported.

References

NIST SP 811. Guide for the Use of the International System of Units (SI).
ISO 80000 quantities and units series.
IEEE/ASTM SI 10. American National Standard for Metric Practice.
BIPM. The International System of Units (SI), 9th ed.

How Engineers Convert Between Unit Systems

Assumptions

Limitations

Engineering checks