🔄 Converter Tools

Free Online Converter Tools — Currency, Units, Dates and Data Formats

Conversion tasks show up everywhere: checking a price in your home currency while shopping abroad, converting a recipe's measurements from cups to grams, calculating the exact number of days between two contract dates, or transforming a CSV export into JSON for an API integration. Each of these is a simple lookup or calculation individually, but manual conversion is a common source of small, avoidable errors — especially where rounding, unit systems, or date-math edge cases like leap years are involved.

This collection of 15 tools handles currency exchange, measurement units, date and time calculations, and structured data format conversion — all instantly, all free, all processed in your browser.

Currency and Unit Conversion: Getting the Small Details Right

Exchange rates float continuously based on global market conditions, and the rate you see on a converter is typically close to the mid-market rate — not the retail rate you'll actually receive at an airport currency exchange counter or via a credit card foreign transaction. Understanding this distinction matters for budgeting: our Currency Converter gives you an accurate reference point for what something costs in your home currency, while actual retail rates typically include a markup of anywhere from under 1% (card payments) to 5–10% (airport kiosks). For a complete breakdown of how to get the most favourable rates while travelling or shopping internationally, read our currency and unit conversion guide.

Unit conversion carries its own set of easy mistakes, particularly around temperature (which requires an offset calculation, not just a multiplication factor) and volume measurements in cooking, where a "cup" is not standardised internationally — the US cup, UK cup and metric cup all differ slightly. Our Unit Converter handles length, weight, volume and temperature across metric and imperial systems with precise, non-rounded results, which matters most in contexts like baking where ratios compound across multiple ingredients.

Date and Time Calculations

Manual date arithmetic is deceptively error-prone because it requires tracking varying month lengths and leap years correctly — a year is a leap year if divisible by 4, except century years, which are only leap years if also divisible by 400. Our Date Difference calculator and Age Calculator handle this automatically, producing exact results for contract terms, notice periods, billing cycles, and age-eligibility calculations. For a full guide to the edge cases that trip up manual date math, see our age and date calculator guide.

For teams working across regions, our Timezone Converter removes the mental math involved in scheduling meetings or setting deadlines across multiple time zones — a persistent source of miscommunication for distributed and remote teams.

Structured Data Format Conversion

Beyond everyday conversions, this category includes a full set of data format converters aimed at developers and analysts moving data between systems that expect different structures. Our CSV to JSON and JSON to CSV converters handle the most common tabular-to-structured translation, useful when importing spreadsheet exports into an API or exporting API data for analysis in Excel. Our XML to JSON and YAML to JSON converters bridge older configuration and data-interchange formats with the JSON that most modern APIs expect. And our Markdown to HTML and HTML to Markdown converters handle the common back-and-forth between documentation formats.

More Converter Tools

Frequently Asked Questions

📰 Related Guides From the Blog

A Quick Reference for Common Conversions

These are useful for quick mental approximations, but for anything requiring precision — baking a recipe with several ingredients, converting a legal document's measurements, or budgeting an international purchase — always use the exact figures from the calculator rather than rounded approximations, since small errors compound across multiple conversions.

When Precision Matters More Than Convenience

Not every conversion needs the same level of accuracy. Converting a hiking trail's distance from kilometres to miles for a rough sense of trip length tolerates significant rounding. Converting a medication dosage, an engineering measurement, or a precise baking ratio does not. In those higher-stakes cases, always use exact figures from a reliable converter and double-check anything where a unit mistake could have real consequences — a lesson that applies as much to currency conversion for a large international payment as it does to a chemistry experiment's measurements.

Data Format Conversion for Developers and Analysts

Moving data between systems that expect different structures is one of the most common friction points in both software development and data analysis work. A client's spreadsheet export needs to become JSON for an API import; an API's JSON response needs to become CSV for analysis in a spreadsheet tool; a legacy system's XML configuration needs modernising to JSON for a new service. Each of these translations is conceptually simple but tedious and error-prone to do manually, particularly with nested or irregular data structures.

The tools in this category handle the most common format pairs automatically, preserving data types and structure correctly rather than requiring manual field-by-field mapping. This matters most with CSV-to-JSON conversion specifically, where CSV's flat, tabular nature has to be interpreted into JSON's potentially nested object structure — getting header detection and type inference right (numbers vs. strings, boolean values, empty fields) is exactly the kind of detail that a purpose-built converter handles more reliably than an ad-hoc script written under time pressure.

International Considerations for Currency and Measurement

For a US, UK or European audience specifically, a few conversion habits are worth building. When shopping from international retailers, remember that displayed prices are frequently before customs duties and import taxes are applied — budgeting an additional 10-25% buffer for these additional costs (which vary significantly by country and product category) avoids an unpleasant surprise at checkout or when a customs bill arrives. When following recipes from a different country, always convert using exact figures rather than memorised approximations, since small rounding errors compound across a multi-ingredient recipe in ways that are more noticeable in baking (where ratios are chemically significant) than in general cooking.

Building Conversion Habits Into Recurring Workflows

If currency or unit conversion is a regular part of your work — an online store pricing products for multiple countries, a freelancer invoicing international clients, a content creator adapting recipes for different regional audiences — it's worth standardising on one trusted converter and one consistent rounding convention rather than re-deciding precision rules every time a conversion comes up. Consistency across a catalogue or a body of content matters more for credibility with your audience than chasing decimal-level precision on any single individual conversion.

Time Zones and Remote Team Coordination

Date and time calculations get an extra layer of complexity once time zones enter the picture. "Today" can mean a different calendar date depending on where you are in the world relative to someone else at the exact same moment, and a deadline specified as "end of day" needs a clearly stated time zone to be unambiguous — "end of day Friday" means something different in New York than in London or Mumbai. International teams coordinating across time zones run into this regularly when scheduling calls or setting shared deadlines. When precision matters across time zones, always specify which zone a date or deadline refers to explicitly, rather than assuming it's obvious from context, and use a dedicated converter rather than mental arithmetic when the stakes are high enough to matter.

Counting Business Days vs. Calendar Days

A common source of confusion in professional contexts is the difference between calendar days and business days. "Net 30" payment terms or a "10 business day" shipping estimate exclude weekends and often public holidays from the count, meaning the actual calendar span is longer than the stated number suggests — ten business days typically spans 14 calendar days, not 10, depending on where weekends fall. Confusing the two is a common cause of missed deadlines and payment disputes, and it's worth explicitly clarifying which type of "day" any business commitment refers to.

Currency Volatility and Larger Transactions

For small everyday purchases, exchange rate movement day-to-day is rarely noticeable. For larger transactions — buying property abroad, paying international tuition, running a business that invoices in a foreign currency — even a small percentage swing in exchange rates can represent a meaningful amount of money. Currencies can move significantly around major economic announcements, so anyone managing a large or recurring international payment is generally better served checking rates regularly in the lead-up to a transaction rather than relying on a single check made weeks in advance.

Keeping Conversions Private

Every converter on Toolzey runs its calculation locally in your browser. Currency amounts, personal dates, and data you paste for format conversion are never transmitted to a server or logged anywhere, which matters particularly for financial figures and any business or personal data you're converting between formats.

Quick Reference for Choosing the Right Converter

Shopping abroad or travelling points toward the currency converter. Cooking, DIY projects or fitness tracking points toward the unit converter. Contracts, deadlines or notice periods point toward the date difference calculator. And moving data between a spreadsheet and an API points toward the structured data converters. Starting from the task rather than the tool name is usually the fastest way to find the right converter for a given situation.