Process & Chemical Calculators
5 free process & chemical calculators — standards-based, with formulas, worked examples, and no sign-up.
Process and chemical engineering starts from a small set of closed-form relations, and this category implements the ones that come up at the bench, in the plant, and in sizing meetings. The ideal gas law calculator solves PV = nRT for any one state variable using the exact CODATA molar gas constant (8.314462618 J/(mol·K), exact since the 2019 SI redefinition), and its density mode turns the same law into ρ = P·M/(R·T) with verified molar masses for air, N₂, O₂, CO₂, and CH₄. The molar mass calculator parses a chemical formula — parentheses, hydrates, and all — over the IUPAC/CIAAW 2021 atomic-weight table and converts molarity and volume into the grams you actually weigh out.
The flow-side tools carry the sizing math. The control valve calculator implements the liquid sizing equation Cv = Q·√(SG/ΔP) and its metric twin Kv (Kv = 0.865·Cv per the IEC 60534 constants), in both directions: the coefficient a duty needs, or the flow an installed valve passes. The NPSH margin calculator checks a pump suction the way a field engineer does — barometric pressure minus vapor pressure from a built-in steam table, plus static head, minus suction friction — and compares the result against the pump's required NPSH. The relief valve tool applies the API 520 Part I orifice-area equations for liquid and critical-gas service and picks the next standard API 526 letter orifice, clearly flagged as preliminary sizing rather than a substitute for the standard.
The boundaries with the neighboring categories are deliberate. Pipe friction, Reynolds number, and duct sizing live in Mechanical and HVAC; open-channel flow, weirs, and water hammer live in Hydraulics; this category owns the questions that need a gas state, a chemical formula, or a process-fitting coefficient. When a valve problem turns into a pipe-network problem, hand the pressure-drop half to the Darcy-Weisbach tools and bring the ΔP back here.
All Process & Chemical Tools
Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, amount, or temperature with the exact CODATA gas constant, plus gas density ρ = P·M/(R·T) with verified air, N₂, O₂, CO₂, and CH₄ molar-mass presets.
Molar Mass & Molarity Calculator
Formula weight from any chemical formula — parentheses, nested groups, hydrates like CuSO4·5H2O — over the IUPAC/CIAAW 2021 atomic-weight table, with per-element breakdown and grams-to-weigh solution prep.
Control Valve Cv & Kv Calculator
Liquid valve sizing both ways: required Cv = Q·√(SG/ΔP) from gpm and psi (or Kv from m³/h and bar), or the flow an installed valve passes, with the verified Kv = 0.865·Cv conversion. Turbulent, non-flashing service.
NPSH Calculator
NPSH available from surface pressure, steam-table vapor pressure and density by water temperature, static head (negative for suction lift), and suction friction — with margin, ratio, and verdict against the pump's NPSHr.
Relief Valve Sizing Calculator
Preliminary PSV sizing per API 520 Part I: liquid A = Q/(38·Kd·Kw·Kc·Kv)·√(SG/ΔP) and gas critical flow with the exact C(k) coefficient, plus API 526 orifice-letter selection D–T with utilization.
Frequently Asked Questions
Which tool do I start with for a gas problem — the ideal gas law or the unit converters?
State first, units second. Establish the gas state with the ideal gas law calculator (absolute pressure, kelvin temperature — the tool converts your °C entry and rejects anything at or below absolute zero), then move the result into whatever unit the downstream calculation wants. The classic trap is feeding gauge pressure into PV = nRT: a 220 kPa gauge reading is about 321 kPa absolute, and the error propagates linearly into density, moles, and every sizing equation that follows.
The valve Cv tool and the relief valve tool both size valves — which one do I need?
Different valves, different physics. The Cv/Kv tool sizes control valves for continuous throttling of liquid flow — how much coefficient a duty needs at a given pressure drop. The relief valve tool sizes the safety device that must dump an emergency flow when pressure exceeds the set point, per the API 520 orifice-area equations. If the question is "what valve passes 50 gpm at 4 psi drop," that is Cv; if it is "what orifice protects this vessel at 110% of set pressure," that is relief sizing — and for final relief design, the standard itself governs.
Why does my pump cavitate even though the NPSH margin looked fine on paper?
Usually because one of the four NPSHa terms was optimistic: vapor pressure rises steeply with temperature (water at 60 °C has ~8.5× the vapor pressure of 20 °C water), suction friction grows with the square of flow, altitude quietly lowers barometric pressure, and the static term flips sign on a suction lift. Re-run the NPSH margin calculator at the real operating temperature and the true maximum flow, and keep a margin — common practice wants at least 0.5–1 m or 10% over the pump's NPSHr, and Hydraulic Institute guidance goes higher for hot or volatile liquids.