Molality converter
Switch a molal concentration between mol/kg, mmol/kg, µmol/kg and mol/g: 1 mol/kg is 1000 mmol/kg and 1 mol/g is 1000 mol/kg. Every step goes through moles per kilogram with fixed factors. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Value
- 1
- From
- mol/kg
- To
- mmol/kg
- Result
- 1,000
- From
- mol_kg
- To
- mmol_kg
- From label
- moles per kilogram
This molality converter turns a numeric molal concentration from one common laboratory or SI unit into another and returns the converted magnitude with canonical unit labels. Conversion always bridges through mol/kg using fixed SI mass factors, so the same input always yields the same result with no network calls, no sampling, and no date-dependent shortcuts. Typical checks include one mole per kilogram to millimoles per kilogram, fifty micromolal to mol per kilogram, and one mole per gram to molal.
Where molality conversion fits in labs, teaching, and software
Colligative-property work often reports freezing-point depression and boiling-point elevation in molal units while analytical methods quote millimolal or micromolal scales, and some densitometry or process sheets list moles per gram, so a single deterministic converter prevents hand-calculator drift when a chemist, technician, or student compares molalities across documents. Lab notebooks convert stock molalities into the unit a cryoscopy protocol expects; quality systems normalize supplier certificates before release; teachers assign homework that needs a fast, offline check of milli and micro prefixes without trusting opaque apps that silently change precision.
Developers call the same contract from scripts to seed deterministic test vectors for product UIs, to normalize user-entered molal concentrations before sizing demos, or to satisfy programming-challenge statements that demand exact SI mass factors rather than a hand-waved estimate. Product tools use the rewrite when a learner or agent types fifty micromolal and the UI must show moles per kilogram and millimoles per kilogram side by side.
Pair it with the molality calculator when you still need m equals n over kilograms of solvent first, and with the molar concentration converter when the same form must also handle volume-based molarity units.
What you can do with it
Colligative property and cryoscopy notes
Convert between mol/kg, mmol/kg, and µmol/kg when comparing freezing-point depression worksheets, boiling-point elevation tables, and analytical methods that mix milli and micro molal scales.
Process and densitometry data
Map moles per gram nameplates into standard molal laboratory units for process sheets, solvent-based models, and deterministic equipment schedules.
FAQ
What does the molality converter cost?
It is free in your browser on this page.
What happens if I send an unknown unit?
Unknown or misspelled units are never silently mapped.
How many mmol/kg is 1 mol/kg?
1 mol/kg is 1000 mmol/kg. Every conversion passes through moles per kilogram with fixed SI factors, so 1 mmol/kg is 0.001 mol/kg and 1 mol/g is 1000 mol/kg.
Does it calculate molality from moles and solvent mass?
No. It only converts a molality you already have from one unit to another. To work out molality from moles of solute and kilograms of solvent first, use the molality calculator.
Do temperature or density affect the result?
No. Molality is moles of solute per mass of solvent, so the converter only multiplies and divides by fixed mass factors. There is no density path and no temperature-dependent model.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/conv/molality \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":1,"from":"mol/kg","to":"mmol/kg"}'const res = await fetch("https://api.kit.forhosting.com/conv/molality", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 1,
"from": "mol/kg",
"to": "mmol/kg"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/molality",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 1,
"from": "mol/kg",
"to": "mmol/kg"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/molality", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":1,"from":"mol/kg","to":"mmol/kg"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":1,"from":"mol/kg","to":"mmol/kg"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/molality", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"value": 1,
"from": "mol/kg",
"to": "mmol/kg"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.molality",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs_value | 1000000000000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Supported units are moles per kilogram, millimoles per kilogram, micromoles per kilogram, and moles per gram, plus everyday aliases such as mol/kg, molal, m, mmol/kg, millimolal, µmol/kg, micromolal, and mol/g.
What the molality converter returns and which units it understands
A molality conversion answers a narrow question: given a magnitude in one moles-of-solute-per-solvent-mass unit, what is the equivalent magnitude in another unit that people actually use in wet labs, physical chemistry, and SI-based engineering reports. This calculator accepts a numeric 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 moles per kilogram, and the fixed factors used for the bridge. Everyday spellings such as mol/kg, molal, m, mmol/kg, millimolal, µmol/kg, micromolal, and mol/g normalize to those ids so forms, query strings, and spreadsheets can reuse the same contract without inventing private enums. Canonical ids are mol_kg for moles per kilogram, mmol_kg for millimoles per kilogram, umol_kg for micromoles per kilogram, and mol_g for moles per gram. There is no approximate density path and no temperature-dependent mass model: the engine either multiplies and divides by fixed factors inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing value, from, or to; non-finite numbers; magnitudes above the documented ceiling; and any unit string that is not on the supported list.
How factors are defined 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 colligative molality. Zero is a valid value and simply yields zero in the target unit. Computation multiplies value by the source factor in moles per kilogram, then divides by the target factor: one millimole per kilogram is exactly one thousandth of a mole per kilogram; one micromole per kilogram is exactly one millionth of a mole per kilogram; one mole per gram is exactly one thousand moles per kilogram because one kilogram is one thousand grams. The preferred fields are value for the molality magnitude, from for the source unit, and to for the target unit, with aliases amount, molality, m, quantity, and n 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. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for value, result, and value_mol_kg, 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 molality conversion fits in labs, teaching, 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.
Integration use cases
Homework and CI fixtures
Generate reproducible molality conversions for worksheets, tutoring software, and unit tests that assert fixed SI mass factors.
Technical questions
Which molality units are supported?
Moles per kilogram (mol_kg / mol/kg / molal / m), millimoles per kilogram (mmol_kg / mmol/kg / millimolal), micromoles per kilogram (umol_kg / µmol/kg / micromolal), and moles per gram (mol_g / mol/g), including common aliases.
How are conversion factors defined?
All conversions bridge through mol/kg: 1 mmol/kg = 0.001 mol/kg, 1 µmol/kg = 1e-6 mol/kg, and 1 mol/g = 1000 mol/kg because 1 kg = 1000 g.
Does this compute molality from moles and solvent mass?
No. This capability converts molality units only. To compute m = n / kg_solvent from amount of solute and solvent mass, use a dedicated molality calculator.