A Notes App That Does the Math As You Type

Most notes apps treat numbers as decoration. You write up a quote — a day rate, some hours, materials, VAT — and the arithmetic happens somewhere else: a calculator on your phone, a spreadsheet in another tab, a guess. Then the job grows by two days, one input changes, and every number below it is quietly wrong. The note still looks finished; the maths inside it went stale the moment you touched it.

Oyren's notes are built around a solve engine — a live calculation layer inside the editor, so the note itself is the calculator. Rates, units and percentages resolve as you write them, and when you change one number, everything that depends on it follows. It's why the Oyren landing page opens on the solve editor and calls it "the most powerful notes engine ever built": that screen isn't a mock-up, it's the product.

What a notes app that does math actually looks like

Here is quote.note, the exact document from Oyren's live demo. Every line is real syntax:

# Studio job, quote
rate = 65 USD
hours = 18.5
labour = rate * hours
materials = 240 USD
travel = 12 miles in km
subtotal = labour + materials
vat = 20% of subtotal
total = subtotal + vat
deposit = 30% of total
balance = total - deposit

As you type, the engine resolves each line in place — the editor's status chip reads solve engine · live:

Three things in that note are beyond a plain text editor. Values have names — labour = rate * hours reads like a sentence, not a cell reference. Units convert inline — 12 miles in km resolves to 19.31 km without you knowing the factor. And percentages are written the way you'd say them — 20% of subtotal, 30% of total — instead of the =B7*0.2 you'd be double-checking in a spreadsheet.

Change one number and the rest follow

The client adds scope and your rate moves from $65 to $75. In a static note, that's seven manual edits and a real chance of missing one. In a solve note, it's one:

There is no formula bar, no drag-to-fill, no "which cells reference B2?" audit. The dependencies are the note's own prose, so the recompute is instant and complete — the balance at the bottom is always the balance.

Versus Notion, Soulver and the spreadsheet tab

Notion is a fine place to write documents, but its maths lives in databases: formula properties, column types, a small expression language attached to tables. If you want vat = 20% of subtotal inside a paragraph of prose, a Notion page can't oblige — the calculation belongs to a grid somewhere else. If you're hunting for a Notion alternative because your notes are full of numbers, this is the difference to test.

Soulver proved a notepad could calculate, and it remains the classic plain text calculator on the Mac — Mac-native and paid. Oyren's solve engine runs in the browser on every platform, and the note it lives in sits inside a full workspace, beside your PDFs, boards and mind maps. As a Soulver alternative it isn't a trimmed-down imitation; it's the same idea with a workspace around it — and notes are on Oyren's free plan.

The spreadsheet will happily do the maths — away from the words that explain it. A quote or an estimate is a document with numbers in it, not a grid with sentences bolted on. When the reasoning lives in A1 notation, the note that justifies it drifts out of date separately, and you end up maintaining two artefacts that disagree.

A writing surface, not a calculator widget

The solve engine is one layer of a proper editor, not the whole product. Notes are .note files in a block editor with LaTeX support, and they live beside the sources they cite — in Oyren's own words, "a proper writing surface that lives beside the source, not in a different product." OCR a scanned PDF into clean Markdown and the numbers you pull from it land in a note that can compute with them — we wrote up that pipeline separately in PDF OCR that keeps the math.

And the entry price is the honest kind: Oyren's free plan is $0 forever and includes notes, mind maps and boards, with 100MB of files. You don't pay to find out whether a calculating notes app fits how you work.

What the solve engine doesn't do

Being straight about the edges, the way we try to be everywhere on this site:

• It isn't a computer algebra system. It evaluates arithmetic, units and percentages as you type; it won't solve for x, expand polynomials or do symbolic calculus.
• It isn't a spreadsheet replacement. Ten named lines that read like sentences beat a grid for a quote; a 400-row model with pivot tables does not belong in a note.
• Its syntax is its own. 20% of subtotal reads like English and takes minutes to pick up, but Excel formulas won't paste in unchanged.

Try it on your next quote

The fastest way to judge a notes app that does the math is to hand it real numbers. Open a workspace, start a note, and type the quote you'd otherwise build in a spreadsheet — a rate, some hours, a percentage or two. Then change a number and watch the rest follow. Get started at oyren.ai/workspaces — notes are on the free plan.