Pressure Calculator
This professional-grade pressure calculator helps students, engineers, and scientists compute: pressure from force and area, force from pressure and area, or hydrostatic pressure. It includes precise unit conversions, clear explanations, and WCAG 2.1 AA accessible design.
Interactive Calculator
Results
Your results will appear here. Unit conversions are included for convenience.
Data Source and Methodology
- BIPM, The International System of Units (SI Brochure), 9th Edition (2019). Retrieved from https://www.bipm.org/en/publications/si-brochure
- NIST, CODATA Recommended Values of the Fundamental Physical Constants (2022). Retrieved from https://physics.nist.gov/cuu/Constants/
- IAPWS, Release on the IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance (IAPWS‑95). Retrieved from https://www.iapws.org
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
The Formula Explained
Core definition:
$$ P = \\frac{F}{A} $$
Rearrangements:
$$ F = P \\cdot A \\quad\\text{and}\\quad A = \\frac{F}{P} $$
Hydrostatic (gauge) pressure:
$$ P_{\\text{gauge}} = \\rho \\; g \\; h $$
Absolute pressure:
$$ P_{\\text{abs}} = P_{\\text{gauge}} + P_{\\text{atm}} $$
SI units: Pa = N/m², 1 bar = 10^5 Pa, 1 atm = 101\,325 Pa, 1 psi ≈ 6\,894.757 Pa.
Glossary of Variables
- P (Pressure): The force applied per unit area. Units: Pa, kPa, MPa, bar, atm, psi, torr.
- F (Force): A push or pull on an object. Units: N, kN, lbf, kgf.
- A (Area): Surface over which the force acts. Units: m², cm², mm², in², ft².
- ρ (Density): Mass per unit volume of a fluid. Units: kg/m³, g/cm³.
- g (Gravity): Acceleration due to gravity. Default standard g = 9.80665 m/s².
- h (Depth): Vertical distance below the free surface. Units: m, ft.
- P_atm (Atmospheric pressure): Ambient pressure. Defaults to 101.325 kPa at sea level.
How It Works: A Step-by-Step Example
Suppose a 500 N force is uniformly applied over an area of 0.02 m². What is the pressure?
- Identify inputs: F = 500 N, A = 0.02 m².
- Apply the definition P = F / A.
- Compute: P = 500 ÷ 0.02 = 25,000 Pa.
- Convert units: 25,000 Pa = 25 kPa ≈ 0.246 bar ≈ 3.63 psi ≈ 0.247 atm × 10 (i.e., 0.247 atm is incorrect here; correct is 25,000 / 101,325 ≈ 0.247 atm).
The calculator performs these steps instantly and lists results across common units.
Frequently Asked Questions (FAQ)
Is pressure always uniform across a surface?
No. Pressure can vary across a surface. The formula P = F/A assumes uniform distribution or uses average values.
What’s the difference between Pa, kPa, MPa, and bar?
They are metric pressure units. 1 kPa = 1,000 Pa; 1 MPa = 1,000,000 Pa; 1 bar = 100,000 Pa.
How do I convert between psi and kPa?
1 psi = 6.894757 kPa. Multiply psi by 6.894757 to get kPa; divide kPa by 6.894757 to get psi.
Should I use gauge or absolute pressure?
Use gauge when comparing to ambient conditions (e.g., tires). Use absolute for thermodynamics or when zero reference must be vacuum.
Does temperature affect hydrostatic pressure?
Indirectly, through density. Warmer fluids are typically less dense, slightly reducing ρgh.
Can I use this calculator for gases?
Yes, the P = F/A relationship is general. For hydrostatics in gases, ρ is small; ρgh may be negligible over modest heights.
What accuracy does the tool use?
Exact arithmetic based on SI definitions and high-precision conversion factors. Display is rounded for readability.