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The best converter I have seen and currently free.
This Unit Converter is a fast and easy to use tool with 18 categories of conversions, including;
✓ Temperature Converter
✓ Mass Converter
✓ Length Converter
✓ Speed Converter
✓ Volume Converter
✓ Area Converter
✓ Energy Converter
✓ Fuel Converter
✓ Angle Converter
✓ Pressure Converter
✓ Time Converter
✓ Digital Storage Converter
✓ Force Converter
✓ Sound Converter
✓ Concentration Converter
✓ Density Converter
✓ Power Converter
✓ Space Converter
✓ Metric to Imperial
If it doesn't convert from Smoot to Sheppy its not worth having.