Unit Conversion Practice Problems- Exercises with Answer Key

Unit Conversion Practice Problems You Can Actually Use

Unit conversions trip up more people than they should. It's not complicated math—it's just multiplication and division with the right numbers. This guide gives you real practice problems with answers, so you can stop second-guessing yourself.

How Unit Conversions Actually Work

Every conversion is a multiplication problem. You take what you have, multiply by a conversion factor, and get what you need. That's it.

The key is setting up your fractions correctly. If you want to convert 5 feet to inches, you multiply by 12 inches/1 foot. The "feet" cancel out, leaving you with inches.

The Golden Rule

Always include your units in calculations. If your final answer doesn't have the right unit, something went wrong. Check your setup.

Practice Problems: Length Conversions

These are the most common ones you'll encounter. Print this section and try them before checking the answers.

Metric Length Problems

Problem 1: Convert 3.5 kilometers to meters

Problem 2: How many centimeters are in 2.7 meters?

Problem 3: Convert 450 millimeters to meters

Imperial Length Problems

Problem 4: How many inches are in 7 feet?

Problem 5: Convert 36 inches to feet

Problem 6: How many yards are in 15 feet?

Mixed Unit Problems

Problem 7: Convert 2.5 miles to kilometers (1 mile = 1.609 km)

Problem 8: How many feet are in 3 meters? (1 meter = 3.281 feet)

Practice Problems: Weight and Mass

People confuse weight and mass in everyday speech. In science, mass is how much matter you have. Weight is the force of gravity on that mass. For most everyday problems, this distinction doesn't matter.

Metric Mass Problems

Problem 9: Convert 4.2 kilograms to grams

Problem 10: How many milligrams are in 0.75 grams?

Problem 11: Convert 2500 grams to kilograms

Imperial Weight Problems

Problem 12: Convert 8 pounds to ounces (1 lb = 16 oz)

Problem 13: How many pounds are in 64 ounces?

Cross-System Problems

Problem 14: Convert 10 kilograms to pounds (1 kg = 2.205 lb)

Problem 15: How many ounces are in 500 grams? (1 oz = 28.35 g)

Practice Problems: Liquid Volume

These show up constantly in cooking, science labs, and anywhere liquids are measured.

Metric Volume Problems

Problem 16: Convert 2.5 liters to milliliters

Problem 17: How many liters are in 750 milliliters?

Problem 18: Convert 0.3 cubic meters to liters (1 m³ = 1000 L)

Imperial Volume Problems

Problem 19: How many cups are in 3 pints? (1 pint = 2 cups)

Problem 20: Convert 8 fluid ounces to cups (1 cup = 8 fl oz)

Cross-System Volume Problems

Problem 21: How many liters are in 5 gallons? (1 gallon = 3.785 L)

Problem 22: Convert 250 milliliters to fluid ounces (1 fl oz = 29.57 mL)

Practice Problems: Temperature

Temperature conversions are trickier because the scales don't line up at zero. You need to add or subtract before multiplying.

Problem 23: Convert 98.6°F to Celsius. Formula: C = (F - 32) × 5/9

Problem 24: Convert 37°C to Fahrenheit. Formula: F = C × 9/5 + 32

Problem 25: Convert -40°C to Fahrenheit

Problem 26: Convert 350°F to Celsius

Practice Problems: Time and Speed

Problem 27: How many seconds are in 4.5 minutes?

Problem 28: Convert 7200 seconds to hours

Problem 29: A car travels 120 miles in 2 hours. What is its speed in mph?

Problem 30: Convert 90 km/h to mph (1 km = 0.621 miles)

Answer Key

No cheating until you've tried. Here's the full solution breakdown:

Length Answers

• Problem 1: 3.5 km × 1000 = 3500 m
• Problem 2: 2.7 m × 100 = 270 cm
• Problem 3: 450 mm ÷ 1000 = 0.45 m
• Problem 4: 7 ft × 12 = 84 inches
• Problem 5: 36 in ÷ 12 = 3 ft
• Problem 6: 15 ft ÷ 3 = 5 yards
• Problem 7: 2.5 × 1.609 = 4.02 km
• Problem 8: 3 × 3.281 = 9.84 ft

Weight and Mass Answers

• Problem 9: 4.2 kg × 1000 = 4200 g
• Problem 10: 0.75 g × 1000 = 750 mg
• Problem 11: 2500 g ÷ 1000 = 2.5 kg
• Problem 12: 8 lb × 16 = 128 oz
• Problem 13: 64 oz ÷ 16 = 4 lb
• Problem 14: 10 × 2.205 = 22.05 lb
• Problem 15: 500 ÷ 28.35 = 17.64 oz

Volume Answers

• Problem 16: 2.5 L × 1000 = 2500 mL
• Problem 17: 750 mL ÷ 1000 = 0.75 L
• Problem 18: 0.3 × 1000 = 300 L
• Problem 19: 3 × 2 = 6 cups
• Problem 20: 8 ÷ 8 = 1 cup
• Problem 21: 5 × 3.785 = 18.93 L
• Problem 22: 250 ÷ 29.57 = 8.45 fl oz

Temperature Answers

• Problem 23: (98.6 - 32) × 5/9 = 66.6 × 5/9 = 37°C
• Problem 24: 37 × 9/5 + 32 = 66.6 + 32 = 98.6°F
• Problem 25: (-40 × 9/5) + 32 = -72 + 32 = -40°F (same on both scales!)
• Problem 26: (350 - 32) × 5/9 = 318 × 5/9 = 176.7°C

Time and Speed Answers

• Problem 27: 4.5 × 60 = 270 seconds
• Problem 28: 7200 ÷ 3600 = 2 hours
• Problem 29: 120 ÷ 2 = 60 mph
• Problem 30: 90 × 0.621 = 55.9 mph

Quick Reference Conversion Table

Bookmark this. You'll need it.

How to Get Better at This

Practice. That's the only way. Here's what works:

• Do 5 conversions before breakfast. Make it a habit. After two weeks, you'll do them without thinking.
• Check your units in every problem. If you end up with seconds × meters, you messed up.
• Use dimensional analysis. Write out your fractions. It looks slow, but it prevents almost every error.
• Memorize the common ones: 1 inch = 2.54 cm, 1 lb = 454 g, 1 L = 0.264 gal. These come up constantly.

Common Mistakes to Avoid

Forgetting to flip the conversion factor. If you need to go from small to big units, you divide. Going from big to small? Multiply. Always.

Screwing up temperature formulas. Remember: you subtract 32 before multiplying by 5/9 when going Fahrenheit to Celsius. Add 32 after multiplying by 9/5 when going the other way.

Using the wrong conversion factor. Check your reference. Some fields use slightly different values. Medical and scientific contexts often use more precise numbers.

Dropping units mid-calculation. Keep them in there. It's your built-in error checker.

When You'll Actually Use This

Cooking from foreign recipes. Calculating shipping weights. Understanding medical dosages. Reading scientific papers. Figuring out if a speed limit sign abroad is faster or slower than what you're used to.

It's not glamorous. But it works.