Unit Converters
Weight Converter
Convert mass units with avoirdupois and ton distinctions.
Enter the values and review the result.
Enter a mass and choose source and target units.
Quick answers
What this calculator answers
- Scope: Converts among nine clearly labeled SI, avoirdupois, U.S. customary, and Imperial mass units.
- Method: Converts the source value to kilograms, then derives the selected target from one authoritative factor per unit.
- Distinction: Separates metric tonne, US short ton, and Imperial long ton, and does not mix troy or force units into the workflow.
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Results depend on the values you enter and any simplified assumptions used by the tool. Verify important results before making decisions or submitting official information.
Reference check
Sources and references
These references provide background context for the topic. They do not replace official advice or documents for personal decisions.
- NIST Guide to the SI, Appendix B: Conversion Factors
National Institute of Standards and Technology
- NIST Guide to the SI, Appendix B.8: Factors Listed Alphabetically
National Institute of Standards and Technology
- The International System of Units (SI Brochure)
Bureau International des Poids et Mesures
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Enter a non-negative mass using a complete decimal or scientific-notation value.
Choose explicitly named source and target units, or use Swap without replacing the amount.
Read or copy the canonical result and review the kilogram-based calculation.
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Related Guides
Background reading and explanations related to Weight Converter.
Frequently Asked Questions
Common questions about Weight Converter and how to read the result.
Does Weight Converter calculate mass or force?
It converts mass units. Weight is the familiar everyday route name, but the calculator does not calculate gravitational force, pound-force, kilogram-force, or newtons.
Which ounce and pound are used?
The selectors explicitly use the avoirdupois ounce and avoirdupois pound used for everyday goods. A troy ounce is different and belongs to precious-metal workflows.
How are the three tons different?
A metric tonne is 1000 kilograms, a US short ton is 2000 avoirdupois pounds, and an Imperial long ton is 2240 avoirdupois pounds.
Can I convert stone?
Yes. One stone is exactly 14 avoirdupois pounds under the factors used here.
Why are troy ounces excluded?
Troy mass is used in specialist precious-metal contexts and is not interchangeable with an everyday avoirdupois ounce. This page keeps the systems clearly separated.
Can mass be negative?
No. Zero is accepted, including a normalized -0, but ordinary negative mass is rejected.