Gibbs free energy calculator

What Gibbs free energy means and what the response contains

Gibbs free energy is the state function that tells you whether a process can proceed spontaneously at constant temperature and pressure. The fundamental combination ΔG equals ΔH minus T times ΔS folds the heat of reaction and the entropy-driven term into a single energy-like quantity with a clear sign rule: negative ΔG favors the forward process, positive ΔG favors the reverse as written, and zero marks equilibrium. This calculator implements that closed form only. It returns the normalized enthalpy, entropy, and temperature you supplied, the product T times ΔS as t_delta_s so you can audit the intermediate, the free-energy change gibbs rounded to the requested precision, a boolean spontaneous flag that is true when ΔG is negative, false when positive, and null when the result is at equilibrium within a tiny numeric epsilon, a string spontaneity tag of spontaneous, non_spontaneous, or equilibrium, the precision used, the method tag gibbs_from_enthalpy_entropy, the formula string ΔG equals ΔH minus T times ΔS, and a short unit_note reminding you to keep energy scales consistent. There is no approximate CAS path and no random sampling of conditions: the engine either builds a finite ΔG inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing enthalpy, entropy, or temperature, non-finite values, magnitudes above the documented ceiling, and any temperature that is strictly negative on the absolute kelvin scale.

How enthalpy, entropy, and temperature are read and stay reproducible

Optional leading plus signs and scientific notation on numeric strings are allowed when they parse as finite decimals; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a clear message so a bad cell does not become a wrong free-energy value. Zero entropy or zero enthalpy is valid and simply yields a pure temperature or pure enthalpy contribution. The preferred fields are enthalpy for ΔH, entropy for ΔS, and temperature for absolute T in kelvin, but aliases such as delta_h, dH, and enthalpy_change for enthalpy, delta_s, dS, and entropy_change for entropy, and T, temp, kelvin, and temp_k for temperature are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. Temperature must be non-negative: if T is less than zero, the request fails with invalid_input because negative absolute temperature is non-physical for this relation and would silently invert the sign of the TΔS term in a misleading way. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for all numeric fields, defaulting to ten and capped at fifteen so JSON goldens stay stable. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing the free-energy formula yourself.

Where ΔG fits in study, lab work, and software

On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split—free interactive exploration and a priced, identical API—matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result. Pair it with molar-enthalpy or equilibrium tools when you need related thermo steps, and with other chemistry endpoints when you are building a small lab of free, deterministic reaction helpers.