🧮 MathNote — Expense Calculator Plugin for Joplin

A Mathematical Calculator + Note taking expense calculator that lives inside your Joplin notes. Write natural expense lines, hit Calculate, and totals appear automatically — no spreadsheet needed.

Table of Contents

• What It Does
• Installation
• Toolbar Buttons
• How to Write Expense Lines
• Line Types Reference
  • expr — Expression Line
  • total — Section Total
  • grandtotal — Grand Total
  • vardef — Variable Definition
  • heading — Markdown Heading
  • blank — Empty Line
  • text — Plain Text
• Operators
• Full Example Note
• The Live Panel
• Tips & Tricks

What It Does

| Before (you type) | After (plugin calculates) | |---|---| | Coffee 3.5 * 20 \| | Coffee 3.5 * 20 \| 70 | | Rent 12000 \| | Rent 12000 \| 12,000 | | Total \| | Total \| 12,070 |

• Every line ending with | is treated as a calculation slot.
• The panel (sidebar) shows a live 75 / 25 split view — expression on the left, result on the right — updating as you type.
• The toolbar button writes calculated results back directly into your note body.

Installation

1. In Joplin, open Tools → Options → Plugins.
2. Click Install from file and select the .jpl file, or search for MathNote in the plugin marketplace.
3. Restart Joplin when prompted.
4. Two new buttons appear in the note toolbar (top of the editor).

Toolbar Buttons

There are two buttons added to the note toolbar:

🧮 Toggle Expense Panel

Command name: mathNote.togglePanel

Opens or closes the live 75/25 split panel in the sidebar. The panel reads your current note and displays every line as a two-column view:

┌─────────────────────────────────┬──────────┐
│  Expression                     │  Result  │
├─────────────────────────────────┼──────────┤
│  Coffee  3.5 * 20               │  70      │
│  Groceries  50 + 30 * 2         │  110     │
│  TOTAL                          │  180     │
└─────────────────────────────────┴──────────┘

The panel updates automatically every time the note content changes — you do not need to click anything to refresh it.

💰 Calculate Expenses

Command name: mathNote.calculate

Evaluates every calculation line in the note and writes the results back into the note body next to the | character.

• Results are aligned at a fixed pipe column so everything lines up neatly.
• Safe to run multiple times — results are always recalculated fresh, never accumulated.
• Shows a toast notification when done: ✓ Expenses calculated and saved.

How to Write Expense Lines

The basic pattern for any expense line is:

[Optional Label]  [Math Expression]  |

The | (pipe character) at the end marks a line as a calculation slot. Without |, the line is treated as plain text and ignored.

Groceries  50 + 30 * 2     |        ← will be calculated
This is just a note                  ← ignored, no pipe

Spacing is flexible — the plugin finds the first digit and treats everything before it as the label.

Line Types Reference

expr — Expression Line

Any line containing a math expression followed by |.

Pattern: [Label] [expression] |

Coffee  3.5 * 20           |        → Coffee  3.5 * 20           | 70
Rent    12000              |        → Rent    12000              | 12,000
Taxi    150 + 80 + 60      |        → Taxi    150 + 80 + 60      | 290
Snacks  (20 + 15) * 3      |        → Snacks  (20 + 15) * 3      | 105

• The label is everything before the first digit (Coffee, Rent, etc.).
• The expression is the numeric math part.
• Existing results after | are automatically replaced on recalculation — safe to re-run.

total — Section Total

A line containing only the word total (or subtotal, sum) followed by |. Sums all expr lines above it since the last heading or previous total.

Keywords: total, Total, TOTAL, subtotal, sum — case-insensitive.

Coffee     3.5 * 20    |        → | 70
Groceries  50 + 30     |        → | 80
Rent       12000       |        → | 12,000
Total                  |        → | 12,150

After a Total line, the section sum resets to zero — the next Total will only include lines written after it.

# Week 1
Lunch    120 + 90    |          → | 210
Dinner   200         |          → | 200
Total                |          → | 410   ← only Week 1

# Week 2
Lunch    100 + 80    |          → | 180
Dinner   150         |          → | 150
Total                |          → | 330   ← only Week 2

grandtotal — Grand Total

A line containing grand total (or overall total) followed by |. Sums all Total values in the note.

Keywords: grand total, Grand Total, GRAND TOTAL, overall total — case-insensitive.

# Food
Groceries  500     |            → | 500
Total              |            → | 500

# Transport
Metro      50 * 22 |            → | 1,100
Uber       300     |            → | 300
Total              |            → | 1,400

Grand Total        |            → | 1,900

Note: Grand Total adds up Total lines only — it does not double-count individual expr lines.

vardef — Variable Definition

A line of the form name = value (no | needed). Defines a reusable variable that can be referenced by name in any expr line that follows it.

Pattern: variableName = [expression]

tax = 0.18
discount = 0.10
item_price = 2500

Shirt     item_price * (1 - discount)       |    → | 2,250
Tax due   item_price * tax                  |    → | 450

• Variable names must start with a letter or _ and contain only letters, digits, and _.
• Variables can reference previously defined variables.
• Variable lines themselves are displayed in the panel but not given a pipe result in the note.

rate = 50
hours = 8
days = 5

Weekly pay  rate * hours * days    |    → | 2,000

heading — Markdown Heading

Any standard Markdown heading (#, ##, ###, etc.). Headings visually group sections in the panel and reset the running section total — so a Total after a heading will only include lines since that heading.

# Monthly Budget

# Food & Groceries
Vegetables  200    |
Fruits      150    |
Total              |      ← sums only Food & Groceries section

# Entertainment
Movies  500        |
Games   300        |
Total              |      ← sums only Entertainment section

blank — Empty Line

A completely empty line. Displayed as a small gap in the panel for readability. Has no effect on calculations.

Coffee  120    |

Rent    8000   |      ← blank line above is just spacing, no impact

text — Plain Text

Any line that has no | and is not a variable definition, heading, or blank. These lines are completely ignored by the calculator and passed through unchanged. Use them freely for notes, comments, or context.

## August Expenses
Note: includes the weekend trip to Pune

Petrol    500 + 200    |    → calculated normally
Hotel     3500         |    → calculated normally

Remember to claim petrol reimbursement from office.   ← plain text, ignored

Operators

| Operator | Symbol | Example | Result | |----------|--------|---------|--------| | Addition | + | 100 + 50 | 150 | | Subtraction | - | 500 - 80 | 420 | | Multiplication | * | 3.5 * 20 | 70 | | Division | / | 1500 / 3 | 500 | | Modulo | % | 100 % 30 | 10 | | Exponentiation | ^ | 2 ^ 10 | 1,024 | | Grouping | ( ) | (50 + 30) * 2 | 160 |

All standard operator precedence rules apply (* and / before + and -). Use parentheses to control order.

(500 + 200) * 0.18     |    → | 126      ← tax on combined amount
500 + 200 * 0.18       |    → | 536      ← tax on 200 only (precedence)

Full Example Note

Here is a complete monthly expense note using every feature:

# Monthly Expenses — August 2025

gst = 0.18
discount = 0.05

---

## 🥗 Food

Groceries      50 + 30 * 2 + 10   |
Eating out     120 * 4             |
Coffee         3.5 * 20            |
Total                              |

## 🚗 Transport

Metro pass     550                 |
Petrol         80 * 6              |
Uber rides     150 + 200 + 90      |
Total                              |

## 🛍️ Shopping

Clothes        2500 * (1 - discount)  |
Books          400 + 350              |
Electronics    8000                   |
Total                                 |

---

Grand Total                        |

After clicking 💰 Calculate Expenses:

# Monthly Expenses — August 2025

gst = 0.18
discount = 0.05

---

## 🥗 Food

Groceries      50 + 30 * 2 + 10       | 120
Eating out     120 * 4                 | 480
Coffee         3.5 * 20                | 70
Total                                  | 670

## 🚗 Transport

Metro pass     550                     | 550
Petrol         80 * 6                  | 480
Uber rides     150 + 200 + 90          | 440
Total                                  | 1,470

## 🛍️ Shopping

Clothes        2500 * (1 - discount)   | 2,375
Books          400 + 350               | 750
Electronics    8000                    | 8,000
Total                                  | 11,125

---

Grand Total                            | 13,265

The Live Panel

The 🧮 Toggle Expense Panel opens a sidebar panel that shows the same note in a clean 75/25 split layout. It is read-only — editing happens in the note itself.

• Left column (75%) — shows the label and expression.
• Right column (25%) — shows the calculated result, right-aligned.
• Section Totals are highlighted in amber.
• Grand Total is highlighted in green.
• Headings are styled in blue and visually group sections.
• Variable definitions appear in a dimmed style — they are context, not expenses.
• The panel refreshes automatically — no manual action needed while typing.

Tips & Tricks

Re-run freely — the calculator strips old results before recalculating, so clicking 💰 Calculate multiple times is always safe.

Labels are optional — a bare expression works just fine:

500 + 200    |    → | 700

Decimals work — use . as the decimal separator:

Fuel  1.5 * 92.50    |    → | 138.75

Variables carry down the note — define once, use anywhere below:

price = 999
quantity = 12

Subtotal   price * quantity         |    → | 11,988
Discount   price * quantity * 0.10  |    → | 1,198.80

Use headings to separate months or categories — each # heading resets the section accumulator, so your Total lines stay accurate even in long notes.

The panel works even before you calculate — open the panel while typing to preview results live without modifying the note body.

License

MIT — free to use, modify, and distribute.