The exact pound definition
The international avoirdupois pound is defined as exactly 0.45359237 kilograms. That one relationship also gives 453.59237 grams per pound. Within the avoirdupois system, 16 ounces make one pound, while 14 pounds make one stone.
See the pound-to-kilogram formula and examples, or review the complete calculation methodology and sources.
Round at the end
Use the full factor during calculation and round the result once. Repeatedly rounding intermediate values can create noticeable differences, especially across many items. A display may show six decimals even when the original scale only supports one; match the final precision to the source measurement and the decision you are making.
Mixed pounds and ounces are not decimals
Eight ounces is 8/16, or 0.5 pound. That means 10 lb 8 oz is 10.5 lb—not 10.8 lb. Use separate fields when your scale provides a mixed reading.
Convert pounds and ounces together.
Pick the tool that matches the unknown
If total price and weight are known, calculate price per pound. If price per pound and quantity are known, calculate total cost. Starting with the right unknown keeps the input form simple.
Context still matters
A mathematically correct conversion does not replace airline baggage rules, carrier billing rules, calibrated laboratory measurement, or professional advice. Use the conversion as one input to the real-world decision.