Hardness conversion

Everyday aliases such as mg/L, gpg, grains, °dH, °fH, and Clark are accepted so lab printouts, softener manuals, and spreadsheet cells share one contract.

What hardness conversion returns and which units it understands

Hardness conversion answers a reporting question, not a treatment question: given a hardness magnitude in one laboratory or plumbing unit, what is the equivalent magnitude in another unit that a municipal certificate, softener table, or export datasheet actually uses. This calculator accepts a finite non-negative value, a source unit, and a target unit, then returns the converted result rounded to a stable precision, the canonical from and to identifiers, human-readable labels, the intermediate value in parts per million as calcium carbonate, and the published factors for grains per gallon and each degree scale. Everyday spellings such as mg/L, grains per gallon, °dH, °fH, Clark, mmol/L, and meq/L normalize to those identifiers so forms, query strings, and spreadsheets can share one contract without private enums. Canonical identifiers are ppm for parts per million, mg_l for milligrams per liter, gpg for grains per US gallon, dh for German degrees, fh for French degrees, eh for English Clark degrees, mmol_l for millimoles per liter, and meq_l for milliequivalents per liter. There is no temperature correction and no soft-versus-hard classification: the engine either multiplies and divides by the documented ppm factors inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include a missing value, from, or to field; non-finite numbers; magnitudes above the documented ceiling; negative hardness; and any target unit that is unsupported.

How the ppm bridge is applied and how results stay reproducible

Optional scientific notation on the value string is allowed when it parses as a finite decimal; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a clear message so a bad cell does not become a wrong softener setpoint. Zero is a valid value and simply yields zero in the target unit. Computation multiplies value by the source factor in parts per million, then divides by the target factor: one grain per gallon is 17.1 ppm, one German degree is 17.8 ppm, one French degree is 10 ppm, one Clark degree is 14.3 ppm, one millimole per liter is 100 ppm, and one milliequivalent per liter is 50 ppm, while ppm and mg/L share a one-to-one ratio. One hundred parts per million therefore becomes one hundred divided by 17.1 grains per gallon, and ten German degrees becomes ten times 17.8 divided by ten French degrees. The preferred fields are value for the hardness magnitude, from for the source unit, and to for the target unit, with aliases amount, hardness, n, quantity, and level for the value, unit, from_unit, source, and input_unit for from, and target, to_unit, output_unit, and into for to so heterogeneous clients can share one contract. Negative values fail with invalid_input because physical hardness cannot be negative. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for value, result, and value_ppm, 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 unit tables yourself.

Where hardness conversion fits in plumbing, labs, 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.