What is 20% of 150? (Answer + Quick Mental Math)
Quick answer: 20% of 150 is 30.
How to calculate 20% of 150
20% is one of the easiest percentages to do in your head — once you see the trick, you'll never forget it. Here are three methods, from fastest to most foolproof.
Method 1: The "divide by 5" trick (fastest)
20% is the same as 1/5. So 20% of any number is just that number divided by 5:
This is the trick servers and bartenders use for fast tip math. Want to know 20% of $87? Divide by 5: $17.40. Done.
Method 2: The decimal formula (most reliable)
Works on any calculator without needing a % button. Just convert 20% to 0.20 (move the decimal two places left) and multiply.
Method 3: Find 10% first, then double it
- 10% of 150 = 15 (move the decimal one place left)
- 20% = 10% × 2 = 15 × 2 = 30
This one's great when 10% gives you a clean number — which it almost always does.
Where you'll see 20% of 150 in real life
- Restaurant tip: A $150 dinner check with a 20% tip = $30 gratuity, $180 total.
- Sale price: A $150 item at 20% off saves you $30; you pay $120.
- Tax: 20% VAT on a £150 purchase adds £30, total £180.
- Down payment: 20% down on a $150,000 starter home = $30,000 down.
- Body fat estimate: For a 150 lb person at 20% body fat, that's 30 lb of fat mass.
The general formula for any "X% of Y"
Quick variations you can sanity-check against 20% of 150 = 30:
- 20% of 100 = 0.20 × 100 = 20
- 20% of 75 = 0.20 × 75 = 15
- 25% of 150 = 0.25 × 150 = 37.50
- 20% of 1,500 = 0.20 × 1,500 = 300
Mental-math shortcuts for the four most common tip percentages
If you can do 10% in your head, you can do all of these:
- 10% tip on $150 = $15 (just move the decimal)
- 15% tip on $150 = $22.50 (10% + half of 10%)
- 18% tip on $150 = $27 (10% × 2, then subtract 10% of that)
- 20% tip on $150 = $30 (just double 10%)
Frequently asked questions
Is 20% the same as one fifth?
Yes. 20/100 = 1/5. Anytime you see 20%, you can mentally substitute "divide by 5" and it'll be faster than the decimal formula. 20% of 250 = 250/5 = 50. 20% of 1,000 = 1,000/5 = 200.
What's a fair tip at a restaurant — 15% or 20%?
In the United States, 20% has become the new standard for sit-down service; 15% is now considered the floor. 18% is a sensible default. For takeout, 10% or a flat $2–5 is normal. International norms vary widely — see our tip calculator for a country-by-country reference.
How do I calculate 20% off a price after sales tax has been added?
Apply the discount to the pre-tax price, then add tax to the discounted price. Most US retailers do it this way at checkout — taxing the marked-down price rather than the original. If you only have the post-tax total, divide by (1 + tax rate) to get back to pre-tax, then take 20% off.
If 20% of 150 is 30, what is 30% of 150?
30% of 150 is 45. The simplest way: take your 20% answer (30) and add another 10% (which is 15). 30 + 15 = 45. Or use the formula: 0.30 × 150 = 45.
Skip the math next time
If you'd rather not run the formula every time you're at a restaurant or shop, our free percentage calculator handles any "X% of Y" instantly. For tipping with bill-splitting, the tip calculator is purpose-built. Shopping for sale items? The discount calculator shows the final price plus savings.
All three run entirely in your browser — your numbers are never sent to a server.