How to Use UnitLens — Free Online Unit Converter
UnitLens covers 15 measurement categories and 200+ units — from everyday conversions like metres to feet and kilograms to pounds, to specialised units like parsecs, electronvolts, and Rankine. No sign-up, no ads, no server calls.
Search or browse to the right category
Use the smart search bar at the top to jump directly to any converter. Type a value and unit in plain language — "5 miles" opens Length with 5 miles pre-filled, "100 kg" opens Weight with 100 kilograms ready, and "72°F" opens Temperature. Typing a unit name alone also works — try "kilowatt" or "atmosphere". Alternatively, click any category in the left sidebar or use the All Categories button on mobile to browse.
Enter your value and select units
In the converter panel, type your value in the From field and select the source unit from the dropdown. The To field updates instantly with every keystroke. Press the swap button (⇄) to reverse the conversion direction without retyping. Both fields accept typed input — entering a target value and reading back the source is equally supported. All conversions use BIPM and NIST reference factors with 64-bit floating-point precision.
Use the full table, history, and export
Below the main converter, the All Conversions table shows your input converted into every unit in the active category simultaneously — click any value to copy it. The Recent Conversions log stores your last 20 entries with one click to reload any of them. Click Download Table to export a structured .xlsx workbook with the full conversion table, an all-categories summary, and your complete session history.
Most standard unit symbols and abbreviations are recognised without typing the full name. Try kPa, AU, kWh, lbf, GHz, or nmi. Search results rank by match quality — exact symbol matches appear first, then prefix matches, then partial name matches. Hundreds of standard symbols across all 15 categories are supported.
Complete Guide to UnitLens — All 15 Conversion Categories
Every measurement category UnitLens covers, the units in each, and the practical contexts where each category is most useful.
What makes UnitLens different from other online converters
Most online unit converters limit to one category per page, require several navigation clicks to reach the right unit pair, and show only a single conversion result at a time. UnitLens solves all three. Smart search takes you directly to any converter with the value pre-filled from a single natural language input. Simultaneously, the all-conversions table shows every unit in the active category so you can see relative magnitudes at a glance. The Excel export produces a structured workbook with the full conversion table, an all-categories summary, and your session history — a feature no other free unit converter offers.
Every calculation runs entirely in your browser — no data is sent to any server, and the tool works offline after the initial page load. Conversion factors are sourced from BIPM SI standards and NIST references with 64-bit floating-point arithmetic providing approximately 15–16 significant digits of precision.
All 15 conversion categories
1 inch = 2.54 cm · 1 mile = 1.60934 km · 1 kg = 2.20462 lb · 1 fl oz (US) = 29.5735 mL · 0°C = 32°F = 273.15 K · 1 kWh = 3,600,000 J · 1 atm = 101,325 Pa · 1 hp = 745.7 W · 1 nmi = 1.852 km · 1 TB = 931.32 GiB
Key features of UnitLens
Type "5 miles", "100 kg", "72°F", or any unit symbol and land directly in the right converter with the value pre-filled. Hundreds of unit names, symbols, and abbreviations are recognised across all 15 categories.
Every unit in the active category is shown simultaneously — not just the selected pair. Click any value to copy it instantly. Particularly useful for understanding relative magnitudes across a full unit system at once.
Download a structured .xlsx workbook with the full conversion table for the active category, an all-categories summary, and your complete session history — unique among free online unit converters.
Both the From and To fields accept typed input. Swap direction with one button click. Enter the target value and read back the source — useful for scaling recipes, engineering tolerances, and budget estimates.
The last 20 conversions are stored with category, units, values, and timestamp. Click any history entry to reload that exact conversion — useful when returning to the same unit pair during a work session.
All conversion logic runs in the browser. After the initial page load, UnitLens works without any internet connection — reliable on flights, in the field, or during local development without stable connectivity.
Frequently Asked Questions about UnitLens
Common questions about conversion accuracy, offline use, KB vs KiB, fuel economy, and smart search behaviour.