Calculate as You Type

• Plain words on the left, answers on the right — every line is its own calculation
• Type a sentence and Arithmos finds the number: “I spent €350 on cheese”
• Standard math: add, subtract, multiply, divide, exponents and parentheses
• Percentages made simple: “30% of 800”, “20% off 4,200”, “20 percent of 800”
• Fractions in plain words: “half of 500”, “two thirds of 90”, “a third off the rent”
• Name values and reuse them: “rent = $2.5k”, then “rent × 12”
• Refer to any earlier line by its number: “line3 + line4” uses those lines’ results
• Shorthand magnitudes: write 2.5k, 3m, 1.2b
• Spell numbers out if you like: “twenty five”, “1.2 million” — words become numbers
• Running totals: total, sum, average, min, max and count
• Subtotals with a simple === divider — kept separate from your grand total
• A live document total at the foot of every sheet
• Smart Totals: sheets that mix types total by type — dates add up to “3 months, 4 days”, units to “2.5 kg”, and your numbers keep their own total, side by side
• Tag any line by tapping its number — cycle four colours and see a running total for each colour in the footer; swipe to see them all
• New sheets start with a quick example to learn from — switch them off in Settings for a blank page

Currencies & Units

• 30+ world currencies with live exchange rates
• Recognises symbols ($ € £ ¥ ₹ …) and ISO codes (USD, EUR, GBP, JPY …)
• Convert inline with a natural “in”: “$500 in EUR”, “£99 in JPY”
• Length, mass, time and data-size units: “5 kg in lb”, “1 mile in km”, “2 hours in minutes”, “1.5 GB in MB”
• Choose your base currency and pick which currencies to show

Dates

• Write dates the way you say them: “June 9”, “9 June 2026”, “21st June”, “4th Jan 2026”
• “Today”, “now”, “yesterday” and “tomorrow” understood as you type
• Weekdays and casual spans: “this Friday”, “next Friday”, “last Monday”, “in 3 weeks”, “3 weeks ago”
• Date math built in: “June 9 + 5 weeks”, “Dec 1 − 10 days”
• Count the gap between two dates: “Today − 4th Jan” reads as 5 months
• Choose the units with “in”, one or several: “Today − April 2nd in months and days”, “21st June in days”, “in years, months and days”
• Perfect for countdowns and “how long ago” — days, weeks, months and years
• Convert a time across time zones: “3pm New York in London”, “9am Tokyo in Sydney”, “now in Berlin” — by city (daylight-saving aware), abbreviation (EST, JST, IST…) or UTC offset

Money Over Time

• Compound interest & savings growth: “$10,000 after 5 years at 4%”
• Just the interest earned: “interest on $10,000 for 5 years at 4% compounding monthly”
• Pick how often it compounds — yearly, monthly, quarterly, weekly or daily
• Say what period a rate is for: “5,212 for 6 months at 8%/month”
• Loan & mortgage repayments: “monthly repayment on $300,000 over 30 years at 6%”
• Total cost & total interest: “total interest on $300,000 over 30 years at 6%”
• Phrase it any way round — rate before or after the duration: “compound interest on $1,000 at 7% for 3 years”
• Name it: “loan of $10,000 over 6 years at 6%” or “invest $1,000 for 3 years at 7%”
• Hourly earnings and rates: “$75/hour × 80 hours”

Notes & Markdown

• It’s a real notepad too — structure a sheet as you go
• Headings (six levels) that read larger and start fresh sections
• Checklists you can tap to tick off — finished items strike through
• Strike through text with ~~tildes~~ — and choose whether ticked tasks and struck-out amounts count toward your totals
• Tables that total their own columns
• Turn a list into a table — select the lines and tap to lay them out as columns
• Turn a list into tasks — select the lines and tap to make them tappable checkboxes
• Collapse a block of lines — select and fold them into a single row that shows their total; expand any time
• Inline links that render as tappable text
• Line comments for notes the calculator ignores
• Beautiful syntax highlighting, rendered inline as you type
• Matching parentheses light up as you move the cursor, so you can see which brackets pair
• Line numbers and a clean two-pane layout you can toggle

Make It Yours

• Eight hand-crafted themes — Midnight, Paper, Pastels, Terminal, Noir, Solarized, Sunset and Forest
• Each restyles the editor, the syntax colours and the typeface (sans, serif, rounded or monospaced), light or dark
• Build your very own theme with the Theme Maker and a live preview
• Adjustable text size and full Dynamic Type support
• Optional tidy-up that auto-formats your sheet as you write

Built for Every Device

• Native apps for iPhone, iPad and Mac
• On iPad, your sheets and the editor sit side by side — pick a sheet on the left, edit it on the right, with the most recent one open the moment you launch
• Your sheets sync everywhere through iCloud
• The calculator-and-notes layout opens up beautifully on bigger screens
• Plain-text .arithmos files — portable, future-proof, and openable anywhere

Share & Collaborate

• Collaborate live over SharePlay — edit together and see each other’s cursors
• Export a clean, formatted PDF of any sheet
• Open files in place from the Files app