Table Calc

Add spreadsheet-style formulas to your markdown tables. Write =SUM(A1:A5), =B1*C1, or =AVERAGE(A1:A3) directly in any table cell and see the results rendered inline — in both Live Preview and Reading view.

Quick Start

Add {{calc}} on the line immediately above your table to opt it into formula evaluation:

{{calc}}
| Item        | Cost | Qty | Total       |
|-------------|------|-----|-------------|
| LLC filing  | 200  | 1   | =B1*C1      |
| Dev account | 99   | 1   | =B2*C2      |
| Accountant  | 250  | 1   | =B3*C3      |
| **Total**   |      |     | =SUM(D1:D3) |

The plugin hides the {{calc}} marker and adds column letters (A, B, C…) above the header and row numbers on the left so you always know which cell to reference.

Tables without a {{calc}} marker are left completely untouched.

Column and Row Reference

Supported Formulas

Functions

Arithmetic

Mixed

Combine functions and arithmetic freely:

=SUM(A1:A3)*1.1
=ROUND(AVERAGE(B1:B5), 2)
=A1+SUM(B1:B3)

Note: Function arguments must be cell references, ranges, or literal numbers — not inline expressions. Use =ABS(A1) not =ABS(A1-B1).

Error Values

A function that produces #ERR invalidates the whole formula, even when nested inside another function — =SUM(SQRT(-4), 5) is #ERR, not 5.

Formulas in Context

Hover over any result cell to see the original formula. Formulas are stored in the markdown — the plugin only changes how they're displayed.

When you click into a formula cell in Live Preview, the raw formula reappears for editing. Click away and the result renders again.

Example: Budget Tracker

{{calc}}
| Category     | Budget      | Spent       | Remaining   |
|--------------|-------------|-------------|-------------|
| LLC setup    | 500         | 200         | =B1-C1      |
| Dev tools    | 200         | 99          | =B2-C2      |
| Marketing    | 300         | 0           | =B3-C3      |
| **Total**    | =SUM(B1:B3) | =SUM(C1:C3) | =SUM(D1:D3) |

Example: Sales Table

{{calc}}
| Product | Price | Units | Revenue     | Tax (10%)   |
|---------|-------|-------|-------------|-------------|
| Widget  | 29    | 12    | =B1*C1      | =D1*0.1     |
| Gadget  | 49    | 7     | =B2*C2      | =D2*0.1     |
| Totals  |       |       | =SUM(D1:D2) | =SUM(E1:E2) |

Installation

From Obsidian Community Plugins

1. Open Settings → Community Plugins
2. Click Browse and search for Table Calc
3. Click Install, then Enable

Manual Installation

1. Download main.js, manifest.json, and styles.css from the latest release
2. Create a folder: <your vault>/.obsidian/plugins/table-calc/
3. Copy the three files into that folder
4. In Obsidian: Settings → Community Plugins → reload → enable Table Calc

Commands

Access via Cmd+P (Mac) or Ctrl+P (Windows/Linux).

How It Works

Formulas are stored as plain text in your markdown file — the plugin never modifies the source. A MutationObserver watches for rendered tables and evaluates any =formula cells on the fly. Only tables immediately preceded by a {{calc}} paragraph are processed; all others are ignored. In Reading view the cell's display is replaced with the computed result; in Live Preview the raw formula stays visible (tinted, since those cells are natively click-to-edit and rewriting their text would break Obsidian's cursor placement) and the result shows as a tooltip on hover instead.

This means your notes remain portable: open them anywhere and you'll see the raw formulas. Enable the plugin and you see the results.

Testing

npm test runs the automated suite: engine.test.js covers the formula engine directly, and main.test.js exercises processTable's DOM handling (via jsdom) — in particular, that Live Preview never rewrites a formula cell's text (Obsidian's Live Preview tables are natively click-to-edit, and CM6 maps cursor position by walking the cell's rendered text, so any change to it desyncs that mapping and corrupts editing).

test/example-vault-note.md is a manual fixture, not run by npm test. Copy it into any vault with this plugin installed to eyeball formula evaluation, error handling (#ERR/#NAME?), and Live Preview vs. Reading View rendering side by side — every Result cell should match the Expected cell next to it (Section 6 is deliberately the exception).

Limitations

• Column letters support A–Z (26 columns max)
• Circular references are stopped at depth 20 and return 0
• Formulas only evaluate in Live Preview and Reading view, not in Source mode
• Function arguments must be cell references, ranges, or literal numbers — not inline expressions (use =ABS(A1), not =ABS(A1-B1))
• A cell counts as numeric only if it's a complete, well-formed number. 1,234 (thousands separator), 5 apples (trailing text), and the literal text Infinity/NaN are all treated as text, not as the number they might resemble — they're excluded from COUNT. This is intentional: parseFloat in JavaScript would otherwise silently read 1,234 as 1 and the string "Infinity" as the number Infinity.
• Non-numeric cells are handled differently depending on the function: SUM/AVERAGE treat them as contributing 0 (so a stray text cell skews a total or average rather than being skipped). MIN, MAX, MEDIAN, PRODUCT, STDEV, and VAR instead exclude non-numeric cells entirely, since a phantom 0 would distort those results far more severely (e.g. zeroing out an entire PRODUCT, or pulling a MEDIAN/STDEV toward a value no cell actually contains).
• Numbers are standard JavaScript doubles (IEEE 754), the same numeric type spreadsheets like Excel use. Integers beyond 2^53 (~9 quadrillion) lose precision, and results are snapped to 8 decimal places to absorb ordinary binary floating-point drift (e.g. 0.1+0.2 reliably shows 0.3, not 0.30000000000000004)
• ROUND rounds half away from zero (ROUND(2.5,0) → 3, ROUND(-2.5,0) → -3), matching spreadsheet conventions rather than JavaScript's native Math.round (which rounds -2.5 to -2)
• References are positional, not tracked. A2 always means "column A, row 2 of the table as it exists right now" — there's no concept of a formula "belonging" to a row. If you insert, delete, or reorder rows, formula text doesn't shift to compensate, so a formula can silently start pointing at the wrong cells. Re-check (or rewrite) formulas after restructuring a table. This is intentional: the plugin never modifies your markdown source, and auto-shifting references would require doing exactly that

Disclaimer

Table Calc is designed for personal notes, budgets, and quick calculations — the kind of arithmetic you'd otherwise reach for a spreadsheet for. It is not intended for safety-critical, financial-regulatory, or any other high-stakes computation. Results are rendered in-browser using JavaScript's standard IEEE 754 floating-point arithmetic and are subject to the same rounding characteristics as any spreadsheet. Always verify critical numbers independently.

License

MIT