New! Symbulator 9, in beta version, for Python and SymPy
Solve circuits with the letters still in them.
Give Symbulator symbols instead of numbers and it hands back algebra — every node voltage, every element current, every power, in terms of whatever you left unknown. Describe the circuit an element at a time and ask it what you want to know.
What it does
Four analyses, every element you meet in Circuits I and II.
- Analyses
- Direct current and alternating current as phasor analysis, transient in the time domain, and the complex frequency domain. Numerical circuits and, more to the point, symbolic ones.
- Answers
- Voltages at every node; current, voltage drop and power in every element. Real and complex power in AC, and the impedance each source sees looking back into the circuit.
- Equivalents
- Thévenin and Norton equivalents between any two nodes, and two-port parameters in six varieties.
- Elements
- Resistors, inductors, capacitors, mutual inductance, independent and dependent sources of both kinds, ideal operational amplifiers and ideal transformers.
- Expert mode
- Hand it the extra equations a problem gives you — a known current, a
power to be delivered — and it solves for the component values you
don't have. When the mathematics allows several solutions it returns
them all, and a condition like
vs > 0picks the one you meant.
What it will not do
Symbulator simulates linear circuits, so there are no diodes and no transistors. It also will not help with problems that turn on applying a formula selectively rather than solving the circuit through.
And it is not a replacement for your brain. You have to understand circuit theory to use it. That has been the design's stance since the 2001 thesis: learn the manual techniques first, and let Symbulator verify what your own hand found.
More than the answer
Push at the answer until you understand it.
A number on its own teaches nothing. Symbulator 9 will plot it, take the whole system apart with you, and write out the equations your own course would have written.
- Plotting tools
- Time-domain plots, Bode gain and phase on a logarithmic axis, and a sweep of any variable against any other — of an answer, or of a transfer function you type yourself.
- Numerical solver
- Hand the whole system to a numerical sheet: untick an equation, turn a known into an unknown, and watch every answer follow. Ask when a waveform reaches a value, rather than what it is at a given moment.
- By-hand equations
- The system as your course teaches it: Kirchhoff's current law at each node, with supernodes, or his voltage law around each mesh, with supermeshes. Written out, solved on its own, and checked against the engine — for the moment your homework disagrees with the machine and you need to see where.
Learn it
A course, not a manual.
Symbulator is taught the way it was meant to be used — against real problems out of real textbooks, worked through from the first circuit description to two-port parameters.
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Thirteen lessons, with worked problems
Read the documentation
From describing your first circuit to transient analysis, three-phase and two-ports — every lesson worked through against real textbook problems.
learn.symbulator.com
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The documentation and the app, side by side
Read and run at the same time
Every lesson on the left, the live app on the right. Each worked problem carries a link that loads that exact circuit into the app — read the explanation, then run it without typing a character.
learn.symbulator.com/split/
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Three hundred and fifty-four of them, built in
Open a worked problem
Every problem in the tutorial is inside the app already, from twenty textbooks — its question, the figure it was printed with, and the answers to check yours against. Each one has a link of its own, so a problem can be sent to a classmate exactly as you are looking at it.
symbulator.pythonanywhere.com/?lesson=1&entry=1
Made to fit
Your circuit, your language, your machine.
What you type, what you keep, and the tongue you think in.
- Schematics
- Type the circuit and see it drawn — proper symbols, reference marks, polarity dots, and the mesh currents of your own working — laid out from the description alone.
- SPICE
- Translate a circuit to a SPICE netlist and back, so what you solved here runs in the tools everyone else uses.
- Input files
- Save a problem — the circuit, the settings, the plot you set up — as one file, to open again or send to someone.
- In your language
- Thirteen languages, chosen from the ribbon: Spanish, Portuguese, French, German, Chinese, Japanese, Korean, Indonesian, Hindi, Bengali, Ukrainian and Esperanto, beside English.
- Yours to keep
- Install it from the browser or download the zip, and it runs entirely on your own machine — no server, no account, nothing to sign in to. Fifteen colour themes, light and dark.
Start here
Run it in a browser tab, or put it on your own machine.
Symbulator 9 is the current version, built on Python and SymPy. Every route below runs the same program.
Use it
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Nothing to install
Run Symbulator online
Opens in a browser tab and runs straight away, on anything with a screen. The quickest way to try Symbulator, and enough for most coursework.
symbulator.pythonanywhere.com
Or install it, and work offline
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Including phones and tablets
Install from the browser
A web page that installs Symbulator 9 onto your device for you. It is the installer, not the program — once it has done its job, Symbulator runs on your device and needs no connection.
install.symbulator.com
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Unpack it yourself
Download the zip
The same program as a plain archive, to put where you want it. Use this if you would rather see what you are installing, or install it somewhere the browser cannot reach.
symbulator.com/9/local.zip
For developers
The engine underneath, if you want to build on it.
Not needed to use Symbulator — this is for people who want to call it from their own code, or fork it.
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The Python package
pip install symbulator— the core of Symbulator: the description parser, the stamping engine and the solver. It is what powers the app, exposed as a library you can import and call directly.It works in a Jupyter notebook too:
pip install symbulator[notebook]adds cell magics —%%dc,%%ac,%%fd,%%tr— that take a circuit description and set the answers as mathematics. -
The source, on GitHub
Both halves are there — the solver that does the algebra, and the interface that wraps it. Symbulator is now open source under the MIT licence, so ports and derivatives are welcome under the same licence, with attribution.
On a calculator
Symbulator still runs on the calculators it grew up on.
Symbulator was born on the TI-89 in 1999 and took first place at the IEEE Region 9 student paper contest in 2000; versions 7 and 8 keep those calculators current.
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7
TI-89 Titanium Stable
Also the Voyage 200 and the classic TI-89. Transfer
s7.tigto the calculator; Laplace transforms come from Lars Frederiksen's DiffEq alongside it. -
8
TI-Nspire CX II CAS Beta
Transfer
s.tnsand refresh the libraries. Still in beta, so expect the occasional bug.
The logic and its history
Two books: how it works inside, and where it began.
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For the curious: how it works inside
The Internal Logic of Symbulator (2026)
A monograph on the solver: its history from the 1999 TI-89 original to today, its complete logic in annotated pseudo-code — enough to build a simulator of your own — and worked exemplars, including one exam problem solved by the 2001 calculator and the 2026 port with the same answer, digit for digit.
learn.symbulator.com/monograph.pdf
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For the historians: where it began
The Symbulator Book (2001)
The English edition of the 2001 thesis that documented the classic calculator Symbulator — twelve chapters and 89 worked problems, defended for a perfect grade, begun in English by two of its users in 2001 and completed in 2026.
learn.symbulator.com/book.pdf