Free on iOS

Write like a memo,
calculate like a pro

Type variables, units, and currencies like a note —
Calto calculates as you write.

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100% Free No Ads Works Offline
Calto app main screen
Problem

The limitations

🧮

Traditional Calculator

Can't remember intermediate results, lacks context for complex calculations.

📊

Spreadsheets

Uncomfortable on mobile, overly complex for simple calculations.

📝

Note Apps

No calculation features - you end up opening a calculator anyway.

Solution

Calto solves it

coffee = 4500 4,500
lunch = 12000 12,000
dinner = 8500 8,500
daily = sum 25,000
# Converted at live rates
apple = $1 $1
apple + 4 $5
apple in won ≈ ₩1,350

Natural as note-taking

Intuitive calculations with variable names

Context preserved

Reuse previous results as variables

Mobile optimized

Great UX even on small screens

Powerful Features

Skip the complex buttons, just write what you think.
Calto handles the rest.

⚡

Real-time Calculation

Results appear within 16ms as you type. Natural expressions like 20% of 5000, 5% off 100, 2^10, or 17 mod 5 just work.

Learn more →
🏷️

Named Variables

Define variables naturally like "coffee = 4500" and use scale notation like 2.5M or 100k.

Learn more →
📐

Unit Conversion

Supports 50+ units across 10 categories: length, weight, temperature, volume, time, area, angle, speed, data rate, and data storage. Try 100m2 in acre or 45deg in rad.

Learn more →
💱

Currency Operations

Supports 6 currencies (USD, KRW, EUR, JPY, CNY, GBP). Mix operations like 100 USD + 50000 KRW. Convert aggregates with sum in won.

Learn more →

Why not just use what you have?

Each tool does one part of the job. Calto does the whole thing on your phone.

CaltoCalculatorSpreadsheetNotes app
Calculation history —
Named reusable values — —
Mobile-friendly input —
Mixed units & currencies — Formulas —
Live results —
Offline, no account Depends

Perfect for these situations

Make everyday calculations easier with Calto

Travel Budget

Organize flights, hotels, meals at a glance with auto currency conversion

flight = $450
hotel = $120 * 5 → $600
food = $50 * 5 → $250
---
sum in KRW → ₩1,755,000

Quick Meeting Math

Estimate project costs and budget allocation in real-time

development = $30000
design = $8000
marketing = $5000
---
total = sum → $43,000

Shopping Total

Track your cart total and stay within budget instantly

milk = 3.20
eggs = 6.50
fruits = 12.00
---
sum → 21.70

Guides & Examples

Copy a worked example into the app and change the numbers.

See all guides →

All Features, Free for Now

Every feature is currently available for free.
A premium plan may be introduced in the future.

Currently Free
Free all features — currently free
  • Answers as you type — one line at a time, no buttons
  • Name your numbers: "coffee = 4500"
  • Convert units, currencies and crypto in one line
  • Dates, ratios and percentages — just write them
  • Share results as text or an image
  • Unlimited documents, no ads, works offline

A premium plan may be added in the future. Core calculation features will always remain free.

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Frequently Asked Questions

Have questions?

What calculations does Calto support?
Basic arithmetic, percentages (20% of 5000), exponent (2^10), modulo (17 mod 5), discount/markup (5% off 100), parentheses, named variables, scale notation (k/M/B), math functions (sqrt, sin, cos, log, etc.), unit conversion (50+ units across 10 categories), currency operations (6 currencies), date & compound time (2h 5min), ratio & proportion (a : b = c : ?), cryptocurrency (BTC, ETH), and sum/avg aggregation. Learn more →
How do currency operations work?
Store currency in variables like "apple = $1", and perform mixed operations like "$1 + 4 = $5". Currency is automatically preserved in sum/avg, and you can convert with "sum in won". Learn more →
Can I use Korean variable names?
Yes! You can name variables in Korean, like "김치 = 10,000". Write your calculations as naturally as taking notes. Learn more →
Does it work offline?
Yes, all basic calculations and unit conversions work offline. Only exchange rates and cryptocurrency rates require an internet connection.
Is Calto free?
For now, every feature is available for free — real-time calculation, variables, 50+ unit conversion across 10 categories, exponent & mod operators, percentage on/off, share & export, date math, ratio & proportion, cryptocurrency, live exchange rates, unlimited documents, and 6 built-in themes. A premium plan may be introduced in the future, but core calculation features will always remain free.
Is there a text calculator app for mobile?
Yes — Calto is a text calculator for iPhone. Type calculations like notes, use variables, convert units and currencies, all from your phone. It is currently available on iOS only.

Can't find your answer?

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