Boiling point calculator
Get the actual boiling temperature of a solution, not just the rise: water with 1 mol/kg of solute and a Kb of 0.512 boils at 100.512 °C. Water at 100 °C is assumed unless you give another solvent's boiling point. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Molality
- 1
- Kb
- 0.512
- Solvent bp
- 100
- Delta tb
- 0.512
- Boiling point
- 100.512
- Precision
- 10
This boiling point calculator returns the elevated boiling point of a dilute solution from two colligative inputs: molality m and the solvent ebullioscopic constant Kb. The textbook identity is a temperature rise ΔTb equal to Kb times m, added to the pure-solvent boiling point T0 so the result is the actual boiling temperature of the mixture, not only the rise. When you omit T0 the engine uses one hundred degrees Celsius, the normal boiling point of water at one atmosphere, which matches the usual first-year problem. Supply another T0 when the solvent is benzene, ethanol, chloroform, or any liquid whose boiling point is not one hundred. Typical check: water-like Kb of 0.512 K·kg/mol with m of 1 mol/kg yields ΔTb of 0.512 K and an elevated boiling point of 100.512. The path is pure arithmetic: no network, no tables, no random sampling.
What an elevated boiling point is and how Tb = T0 + Kb·m is applied
A non-volatile solute lowers the vapor pressure of a solvent. The liquid therefore has to be heated further before its vapor pressure equals the surrounding pressure, so the boiling temperature of the solution sits above that of the pure solvent.
For an ideal dilute non-electrolyte that rise is linear in the number of solute particles per kilogram of solvent: ΔTb equals Kb times m, where m is molality in moles of solute per kilogram of solvent and Kb is the solvent-specific ebullioscopic constant with units K·kg/mol (numerically the same as °C·kg/mol for a temperature difference). Adding the rise to the pure-solvent boiling point T0 yields the elevated boiling point Tb that a thermometer would read at boiling.
This page uses that two-factor textbook form with an implicit van 't Hoff factor of one; it does not ask you to supply a particle count. When T0 is omitted the engine assumes one hundred, the normal boiling point of water, so a single aqueous homework line such as m equals 1 and Kb equals 0.512 produces Tb equals 100.512 without extra fields. When the solvent is not water you must pass T0 on the same scale you want for Tb, for example 80.1 degrees Celsius for benzene.
Zero molality is allowed and returns Tb equal to T0. Negative molality is rejected because moles of solute per kilogram of solvent cannot be negative under this definition.
Where a boiling point calculator earns its keep in study, lab, and software
Students meet this identity in the first colligative-properties chapter, when a worksheet gives molality and Kb and asks for the boiling temperature of the solution rather than only the rise. Teachers can pre-generate answer keys for modest molalities and published solvent constants without trusting opaque calculator apps that silently insert a van 't Hoff factor or switch from Celsius to kelvin.
Laboratory reports often need the expected boiling point of a prepared non-electrolyte solution before comparing it with a measured value; feeding the same m and Kb that went into the recipe yields a reproducible Tb you can cite. Developers call the contract from scripts to seed deterministic test vectors for chemistry education products, to normalize user-entered colligative inputs before plotting a boiling curve, or to satisfy programming-challenge statements that demand the elevated boiling point rather than a hand-waved estimate.
Process and quality checks sometimes need a fast offline source of Tb so dilute-solution boiling can be validated without opening a full thermodynamics package. Use a dedicated van 't Hoff tool when i is not one, and a freezing-point tool when you need Tf rather than Tb.
What you can do with it
Homework and lab boiling-point checks
Compute the elevated boiling point from molality and solvent Kb before writing lab reports or checking textbook answers that omit a van 't Hoff factor.
Tutoring and chemistry software
Turn user-entered molality and Kb into a stable elevated boiling point for interactive lessons, with water T0 defaulting to 100 °C.
FAQ
What does the boiling point calculator cost?
It is free in your browser on this page.
What happens if molality is negative?
Molality cannot be negative for this colligative definition of boiling-point elevation.
Does this include the van 't Hoff factor i?
No. This calculator uses the textbook non-electrolyte form ΔTb = Kb·m. For electrolytes with i ≠ 1, use a colligative tool that accepts i.
How is the boiling point of a solution calculated?
Multiply the solvent's ebullioscopic constant Kb by the molality to get the rise, then add it to the boiling point of the pure solvent. With a Kb of 0.512 and 1 mol/kg, water goes from 100 to 100.512 °C.
How do I use it for a solvent other than water?
Enter that solvent's own boiling point, on the scale you want for the answer, together with its Kb. For benzene, for example, you would start from 80.1 °C instead of the default 100 °C for water.
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/chem/boiling-point \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"molality":1,"kb":0.512}'const res = await fetch("https://api.kit.forhosting.com/chem/boiling-point", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"molality": 1,
"kb": 0.512
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/boiling-point",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"molality": 1,
"kb": 0.512
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/boiling-point", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"molality":1,"kb":0.512}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"molality":1,"kb":0.512}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/boiling-point", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"molality": 1,
"kb": 0.512
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.boiling_point",
"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 | 1000000000000000 |
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
Use it free in the browser, or call the API at $0.002 per successful request.
What an elevated boiling point is and how Tb = T0 + Kb·m is applied
The response echoes molality, kb, and the T0 that was used, then reports delta_tb, boiling_point, precision, a method tag boiling_point, a short formula string, and a unit of same_as_solvent_bp so the scale of T0 is the scale of Tb.
Input contract, defaults, rounding, and how errors are reported
Magnitudes above the documented ceiling are rejected. Missing molality or kb also fails. Failed validation is not billed. POST a JSON body with two required finite numbers: molality for m and kb for the ebullioscopic constant. Aliases m, b, and molal are accepted for molality, and Kb, ebullioscopic_constant, boiling_constant, and K_b are accepted for the constant, so a spreadsheet column or a query string can reuse the same contract. Optional solvent_bp, with aliases T0, tb0, pure_bp, and solvent_boiling_point, is the boiling temperature of the pure solvent; when it is omitted the engine uses one hundred so aqueous problems do not require a third field. Optional precision, with aliases decimals and dp, chooses how many decimal places to expose for every numeric field, defaulting to ten and capped at fifteen so JSON goldens stay stable across runtimes. Numeric strings with an optional leading plus and scientific notation are accepted when they parse as finite decimals; empty strings, hex prefixes, and non-numeric tokens fail with invalid_input naming the field. The only physical sign rule is on molality: a negative value, including negative zero, fails with a message that molality cannot be negative for boiling point elevation ΔTb equals Kb times m.
Where a boiling point calculator earns its keep in study, lab, 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
Deterministic test fixtures
Generate reproducible boiling_point and delta_tb values for unit tests, property checks, and CI assertions on Tb = T0 + Kb·m.
Technical questions
What formula does this tool use?
ΔTb = Kb · m and Tb = T0 + ΔTb, with implicit i = 1. T0 defaults to 100 °C (water at 1 atm) when solvent_bp is omitted.
Do I have to enter the solvent boiling point?
No. If you omit solvent_bp the engine uses 100, the normal boiling point of water in °C. Pass solvent_bp (or T0) for any other solvent or scale.