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Free Unit Converter.

Convert length, weight, temperature, volume, area, speed and time instantly — type a value and every unit updates live, right in your browser. Nothing here is ever uploaded.

Not uploaded — runs in your browser 7 categories, 40+ units Live two-way conversion No subscription or account
Category
From
To
Quick reference
Nothing here is ever uploaded — it’s all generated right in this browser tab, on your device. There’s no server involved, so we never see it, copy it or keep it.
How it works

Type a value, and every unit updates instantly — no waiting on a server

Altto's unit converter works right in your browser tab, so there's no page reload and no calculation tied to someone else's servers.

01

Pick a category

Choose length, weight, temperature, volume, area, speed or time.

02

Type a value

Enter a number in either field — the other one updates instantly.

03

Copy the result

Use the copy button, or scan the quick-reference table below.

Why this runs in your browser, not on a server

A conversion you’re running is often part of something you haven’t finished yet — a recipe, a spec sheet, a quote for a client. Altto skips uploading it anywhere — every calculation happens entirely on your device.

  • Nothing is uploaded, everEvery conversion is calculated by code that runs in this browser tab, because there’s no server on the other end.
  • No account, no email wallConvert as many values as you like without signing up or handing over an email address.
  • Seven categories in one toolLength, weight, temperature, volume, area, speed and time, all in the same interface — no switching tools.
40+

units across seven categories, one page. No switching between separate converter tools for each unit type.

FAQ

Frequently asked questions

The practical details on how this tool works. Need another free browser tool? See Word Counter.

How accurate are these conversions?
Every conversion uses standard, internationally recognized conversion factors (for example, 1 inch is exactly 2.54cm and 1 mile is exactly 1.609344km). Results are shown to about 6–7 significant figures — more than enough for cooking, DIY, homework or everyday estimates.
Which categories does this tool cover?
Length, weight, temperature, volume, area, speed and time — the seven categories people convert most often. It deliberately doesn't cover specialist units like pressure, energy or torque, which are a different, narrower use case.
Can I convert in either direction?
Yes — type into either the “From” or “To” field and the other one updates automatically, so you don't need to work out the conversion backwards by hand.
What's the quick reference table for?
It shows your currently selected “From” unit converted into every other unit in that category at once, so you can scan a few conversions without re-typing a value each time.
Is my data sent anywhere?
No — every conversion runs entirely inside this browser tab, on your device. There's no server involved at all, so nothing you type is ever seen, copied or kept by Altto.
Do you keep a copy of what I convert?
No. There's no upload or storage involved. See the Privacy Policy for details.
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