How to use the factor-label method
- Write your given value as a fraction over 1.
- Multiply by a conversion factor so the unit you want to cancel appears in the denominator.
- Keep multiplying factors until only your target unit remains.
- Multiply all the numbers on top; divide by all the numbers on the bottom.
| Relationship |
Factor (use either orientation) |
| 1 km = 1 000 m |
1 000 m
1 km
|
| 1 m = 100 cm |
100 cm
1 m
|
| 1 m = 1 000 mm |
1 000 mm
1 m
|
| 1 cm = 10 mm |
10 mm
1 cm
|
| 1 in = 2.54 cm |
2.54 cm
1 in
|
| 1 ft = 12 in |
12 in
1 ft
|
| 1 mi = 1 609 m |
1 609 m
1 mi
|
| Relationship |
Factor (use either orientation) |
| 1 kg = 1 000 g |
1 000 g
1 kg
|
| 1 g = 1 000 mg |
1 000 mg
1 g
|
| 1 lb = 454 g |
454 g
1 lb
|
| 1 lb = 16 oz |
16 oz
1 lb
|
| 1 tonne = 1 000 kg |
1 000 kg
1 tonne
|
| Relationship |
Factor (use either orientation) |
| 1 hr = 60 min |
60 min
1 hr
|
| 1 min = 60 s |
60 s
1 min
|
| 1 day = 24 hr |
24 hr
1 day
|
| 1 year = 365 days |
365 days
1 year
|
| Relationship |
Factor (use either orientation) |
| 1 L = 1 000 mL |
1 000 mL
1 L
|
| 1 mL = 1 cm³ |
1 cm³
1 mL
|
| 1 L = 1 000 cm³ |
1 000 cm³
1 L
|
| 1 m³ = 1 000 L |
1 000 L
1 m³
|
| 1 gal = 3.785 L |
3.785 L
1 gal
|
| 1 cup = 250 mL |
250 mL
1 cup
|
| Relationship |
Factor (use either orientation) |
| 1 kJ = 1 000 J |
1 000 J
1 kJ
|
| 1 cal = 4.184 J |
4.184 J
1 cal
|
| 1 kcal = 1 000 cal |
1 000 cal
1 kcal
|
| 1 kcal = 4 184 J |
4 184 J
1 kcal
|
| Relationship |
Factor (use either orientation) |
| 1 atm = 101 325 Pa |
101 325 Pa
1 atm
|
| 1 atm = 760 mmHg |
760 mmHg
1 atm
|
| 1 atm = 760 torr |
760 torr
1 atm
|
| 1 kPa = 1 000 Pa |
1 000 Pa
1 kPa
|
| Relationship |
Factor (use either orientation) |
| 1 mol = 1 000 mmol |
1 000 mmol
1 mol
|
| 1 mol = 6.022 × 10²³ particles |
6.022 × 10²³ particles
1 mol
|
| 1 mol (gas, STP) = 22.4 L |
22.4 L
1 mol
|
| Relationship |
Factor (use either orientation) |
| 1 m² = 10 000 cm² |
10 000 cm²
1 m²
|
| 1 km² = 1 000 000 m² |
1 000 000 m²
1 km²
|
| 1 m³ = 1 000 000 cm³ |
1 000 000 cm³
1 m³
|
| Relationship |
How to build the chain |
| 1 km/h → m/s |
Multiply by 1 000 m / 1 km then by 1 hr / 3 600 s |
| 1 m/s = 3.6 km/h |
Multiply by 3 600 s / 1 hr then by 1 km / 1 000 m |
| 1 mi/h → m/s |
Multiply by 1 609 m / 1 mi then by 1 hr / 3 600 s |
Tips for multi-step problems
- Compound units (m/s, kg/m³, mol/L) — convert the top and bottom separately by inserting extra factors.
- Area & volume — square or cube the linear factor. 1 m = 100 cm, so 1 m² = 100² cm² = 10 000 cm².
- Check your answer — if you're converting to a smaller unit, your number should get bigger, and vice versa.
- Unit cancellation — every unit in a denominator cancels with the same unit in a numerator above or below it.