Rex says
The fast lane for the math you almost remember from school. Type the numbers, get the answer, move on with your day.
Try a scenario
Click to load — tweak from there.Inputs
Result
log_b(x)
3.000000
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter x.
- 2Enter base.
- 3Read your log_b(x) on the right — it updates as you type.
- 4Hit Share to keep the scenario or send it to someone.
About this calculator
Computes the logarithm of x to any base b using change of base.
Worked example
Using the values the calculator loads with:
Inputs
- x: 1000
- Base: 10
Results
- log_b(x): 3
What each field means
Inputs
- x
- The x used in the calculation. Starts at 1000 so you have a working example on load.
- Base
- The base used in the calculation. Starts at 10 so you have a working example on load.
Results
- log_b(x)
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the log calculator work?
Computes the logarithm of x to any base b using change of base.
What do I need to enter?
2 values: x, and base. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the log_b(x) result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Results are rounded for display; the underlying calculation keeps full precision.
Who is this tool for?
It's built for students, developers, and anyone who needs the answer right now without setting up a spreadsheet.
Accuracy and limitations
- Results are rounded for display; the underlying calculation keeps full precision.
- Very large or very small inputs may hit floating-point limits in the browser.
- Inputs outside the accepted range are clamped rather than rejected.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Logarithm Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/log
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/log" target="_blank" rel="noopener">Logarithm Calculator — RevenueLab</a> (2026).</p>
Source: [Logarithm Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/log) (2026).