Everyday conversion guide
Updated September 16, 2026
A conversion changes the unit used to describe a quantity. It does not change the quantity itself. A 2-meter shelf remains the same shelf when its length is written as approximately 78.74 inches. Start by identifying what you measured and which unit system the original source uses.
Length: feet, inches, and metric dimensions
For inches to centimeters, multiply by 2.54. Reverse the conversion by dividing centimeters by 2.54. For feet to meters, multiply by 0.3048. These factors refer to the international inch and foot.
Will a 36-inch shelf fit a 90-centimeter space?
36 × 2.54 = 91.44 cm. The shelf is 1.44 cm wider than the space, so it will not fit on those measurements alone. Convert both dimensions before comparing them; do not round 91.44 down to 90 just to simplify the comparison.
Mixed feet and inches need a first step. For 5 feet 6 inches, calculate 5 + 6 ÷ 12 = 5.5 feet, then multiply by 0.3048 to obtain 1.6764 meters. Entering 5.6 feet instead describes 5 feet 7.2 inches. Similarly, enter a fractional inch such as 3/8 as the decimal 0.375.
A quick distance estimate is useful before checking a result: a mile is longer than a kilometer, so a distance expressed in kilometers should have a larger numerical value. Five kilometers is about 3.107 miles, not about eight miles. The calculator uses 1 mile = 1.609344 km.
Weight: ordinary ounces, pounds, and kilograms
The Weight tab converts mass, using the everyday naming found on scales and packages. One avoirdupois pound is 0.45359237 kilograms, and one pound contains 16 avoirdupois ounces. A stone contains 14 pounds. Precious-metal troy ounces are a different unit and are not supported here.
A 10-pound parcel
10 × 0.45359237 = 4.5359237 kg, or about 4.536 kg. If a carrier asks for a rounded shipping weight, follow that carrier's rounding rule. The numerical conversion alone does not determine billable weight, which may also depend on the parcel's dimensions.
For a reading of 11 stone 4 pounds, combine the units first: 11 × 14 + 4 = 158 pounds. Then select pounds to kilograms. Entering 11.4 stone would mean 11 stone plus 0.4 of a stone, which is 5.6 pounds.
Volume: check which cup, pint, or gallon
Metric Flip's teaspoon, tablespoon, cup, fluid ounce, pint, quart, and gallon are US customary liquid units. The labels explicitly say US. They are not imperial liquid units, US dry pints, or the rounded measures sometimes printed on nutrition labels.
| US liquid unit | Milliliters |
|---|---|
| Teaspoon | 4.92892159375 |
| Tablespoon | 14.78676478125 |
| Fluid ounce | 29.5735295625 |
| Cup | 236.5882365 |
| Pint | 473.176473 |
| Gallon | 3785.411784 |
Scaling a liquid ingredient
A recipe calls for 1.5 US cups of milk. Multiply 1.5 × 236.5882365 to obtain 354.88235475 mL, about 355 mL. If the recipe instead uses a 250 mL metric cup, the same written amount is 375 mL. The recipe's cup definition matters more than adding another decimal place.
An imperial gallon is 4.54609 liters, compared with 3.785411784 liters for the US gallon used here. If a UK source simply says gallons, establish which definition it means before using the Volume tab. Do not substitute the US option for an imperial measurement.
Why cups cannot become grams directly
Volume tells you how much space an ingredient occupies; mass tells you how much matter it contains. A cup of flour and a cup of honey need not have the same mass. Packing flour more tightly can change the mass without changing the cup's nominal volume. Use an ingredient-specific measured weight or weigh the ingredient; this converter deliberately keeps mass and volume separate.
Temperature: the offset matters
For a temperature reading, use °F = °C × 9/5 + 32. For the reverse direction, use °C = (°F − 32) × 5/9. For kelvin, K = °C + 273.15. Kelvin uses the symbol K without a degree sign.
Reading a 350 °F oven setting
(350 − 32) × 5/9 = 176.666… °C. About 177 °C is the mathematical equivalent. An oven with settings in 10-degree steps may require a nearby setting, but the converter does not adjust for fan-assisted cooking, oven calibration, or recipe timing.
A temperature difference follows a different rule: a rise of 10 °C is a rise of 18 °F. Do not add 32 to a difference. The Temperature tab is intended for absolute readings. Values below 0 K (−273.15 °C or −459.67 °F) are outside the ordinary physical range even though the mathematical formula can still produce a number.
Area: square the length factor
Area has two dimensions. Since one foot is 0.3048 meters, one square foot is 0.3048 × 0.3048 = 0.09290304 square meters. Multiplying square feet by 0.3048 would apply a length conversion to an area and give the wrong result.
A 12-foot by 10-foot room
First find the area: 12 × 10 = 120 ft². Then 120 × 0.09290304 = 11.1483648 m², approximately 11.15 m². This is the floor area, before allowing for cutting waste or the way a flooring product is packaged.
For an irregular room, split the floor into rectangles, calculate each area in the same units, then add them. A hectare is 10,000 m²; an acre is 4,046.8564224 m² in this converter. Old surveys may use a historical survey foot; this tool uses the international foot and is not a land-survey conversion service.
Speed: keep distance and time together
Multiply miles per hour by 1.609344 to get kilometers per hour. Multiply meters per second by 3.6 to get kilometers per hour. A knot is one nautical mile per hour, or 1.852 km/h. It is not a mile per hour.
Understanding an 80 km/h road sign
80 ÷ 1.609344 = approximately 49.71 mph. This provides context when reading a speedometer in a different unit. It does not change the posted limit or account for speedometer error. For a 5 m/s wind reading, 5 × 3.6 = 18 km/h.
Speed is different from pace. Minutes per kilometer cannot be converted to mph by a fixed multiplication factor alone because pace describes time per distance. Fuel economy is another different quantity; miles per gallon is not a speed unit.
Check the result before using it
- Match the measurement type: length to length, volume to volume.
- Check qualifiers such as US, imperial, fluid, square, or troy.
- Combine mixed units before entering a decimal value.
- Check the approximate size and round only at the end.
These examples are Metric Flip's explanations. Unit definitions and conversion factors can be checked against NIST's Guide to the SI, Appendix B. See our calculation method and limitations for how the displayed result is produced.