Notes from the toolbox
Tutorials, tips, and behind-the-scenes posts about the free online tools we make and the people who use them.
The Gizmoop blog covers everything we learn while building free online tools. You will find practical how-to guides for writers (essay word counts, SEO content length, keyword density), social media managers (platform character limits, post length benchmarks), and developers (JSON formatting, regex patterns, Base64 encoding).
We also share productivity workflows, privacy tips, and the occasional deep dive into how a particular tool works under the hood. We never paywall anything.
How Many Miles Is a 5K? Plus 10K, Half, and Full Marathon
A 5K is 3.1 miles. Here is every race distance in miles and km, average finish times, step counts, and how the conversion works.
Average Height for Men and Women (US and Worldwide)
The average height is 5 ft 9 in for US men and 5 ft 4 in for women, with full charts by age and country worldwide.
How Far Is a 10K in Miles? A Runner’s Guide
A 10K is 6.21 miles: split tables, finish times, step counts, a free converter, and a complete beginner training plan.
How Many Miles Is a Marathon, and Why Is It 26.2?
A marathon is 26.2 miles (42.195 km): the crisp answer plus the full history of why the distance is so oddly specific.
What Generation Am I? Birth Years for Every Generation
Find your generation by birth year with a complete chart of every generation from Boomers to Gen Beta, plus 2026 ages.
Oven Temperature Conversion Chart: Celsius, Fahrenheit, Gas Mark
A complete oven temperature conversion chart with Celsius, Fahrenheit, gas mark, fan oven, and air fryer values for every recipe setting.
Race Distance Conversion Chart: 5K to Marathon in Miles and Km
The definitive race distance conversion chart showing every event from 5K to 100K in miles, km, meters, track laps, and finish times.
What Temperature Is a Fever? A Celsius and Fahrenheit Guide
A fever is generally a body temperature of 100.4F (38C) or higher, with thresholds in Celsius and Fahrenheit and by measurement method.
Normal Body Temperature: Ranges in Celsius and Fahrenheit
Normal body temperature is a range near 97.9F (36.6C), not the old 98.6F, and varies by age, time of day, and measurement method.
TV Size Guide: Real Dimensions of 55, 65, and 75 Inch TVs
A TV size is the screen diagonal, not the width: real measured dimensions, stand width, weight, and viewing distance for every size.
How Much Should I Weigh? Healthy Weight by Height and Age
There is no single number. A healthy weight is a range set by height, with a full chart in pounds and kg and the truth about age.
Ideal Body Weight: How to Find Your Healthy Range
Ideal body weight is a formula estimate, not one magic number. Compare the Devine, Robinson, Miller, and Hamwi formulas against your healthy BMI range.
Average Walking Speed by Age (mph, km/h, and Pace)
The average adult walks about 3 mph (4.8 km/h). See average walking speed by age, brisk pace, and a full speed-to-pace table.
What Is a Healthy BMI? Ranges by Age and Gender
A healthy BMI is 18.5 to 24.9, and for adults it is the same for men and women and does not change with age. Here is why.
Height and Weight Chart: Healthy Weight for Your Height
A complete height and weight chart showing the healthy weight range for every height from 4 ft 10 in to 6 ft 6 in, in pounds and kg.
What Size TV for Your Room? Viewing Distance Explained
For a 4K TV, screen size equals viewing distance divided by 1.2. Full tables matching TV size to seating distance for any room.
How to Pay Off a Car Loan Faster: 6 Proven Strategies
Six proven ways to pay off a car loan faster, from biweekly payments to refinancing, each with a worked example of the interest you save.
How Many Pages Is 1,000 Words? (Full Conversion Guide)
1,000 words is about 2 pages single-spaced and 4 pages double-spaced. A full words-to-pages chart and what changes the count.
Word Count by Content Type: Essays, Blogs, Novels, Emails
Every type of writing has a target length. Word counts for novels, essays, blog posts, emails, and speeches in one reference guide.
BMI for Athletes: Why Muscular People Get Misleading Results
BMI can wrongly label a lean, muscular athlete as overweight because it cannot tell muscle from fat. Here is what to use instead.
Generations Explained: Boomers, Gen X, Millennials, Gen Z, Alpha
The living generations span the Silent Generation to Gen Alpha. A full profile of each: birth years, defining events, values, and 2026 ages.
Air Fryer Conversion Chart: Oven Temperature and Time
To convert an oven recipe to an air fryer, drop the temperature 25F and cut the time about 20 percent. Full chart plus cook times.
Normal Temperature for Babies and Newborns
A normal baby temperature is about 97.5F to 100.3F. A fever is a rectal reading of 100.4F or higher, with clear advice on when to call the doctor.
Healthy Weight for Women: Ranges by Height
A healthy weight for a woman is a range set by height, plus the body-composition and life-stage context that charts leave out.
BMI vs Body Fat Percentage: Which Number Matters More
BMI is a fast, free screening number, but body fat percentage measures what actually matters. A full comparison and what to track.
Waist-to-Height Ratio: A Better Health Marker Than BMI?
Keep your waist under half your height. Waist-to-height ratio is a simple health marker that often beats BMI, with a full chart by height.
BMI for Women: Healthy Ranges and What Your Number Means
A healthy BMI for a woman is 18.5 to 24.9, the same as for men, plus the women-specific context: body fat, pregnancy, and menopause.
How Much Should a Woman Weigh? Healthy Ranges by Height
There is no single number. A healthy weight for a woman is a range set by her height, with a full chart and answers for every common height.
How Many Steps Are in a Mile or a Kilometer?
Walking is about 2,000 to 2,500 steps per mile, running about 1,400 to 1,700. Full charts by height and pace, plus steps to miles and km.
How to Pay Off Student Loans Faster
Pay off student loans faster with extra principal payments, autopay discounts, and the avalanche method, each with a worked example.
Leap Year Birthdays: When Do Feb 29 Babies Celebrate?
People born on February 29 celebrate on Feb 28 or March 1 in common years. The rules, the odds, and how leaplings handle birthdays.
How Many Words Is an Essay? Length Guide by Type and Level
Essay length depends on level and type, from a 500-word high school essay to a 5,000-word graduate paper. A full guide with a word-count table.
How Many Words Per Page? Font and Spacing Breakdown
A single-spaced page holds about 500 words, a double-spaced page about 250. How font, size, spacing, and margins change the count.
Is BMI Accurate? What the Science Says in 2026
BMI is a useful screening tool but a weak measure of individual health. What the 2026 science says and what to use alongside it.
How to Lower Your BMI: A Realistic Step-by-Step Guide
Lower your BMI by losing body fat slowly and sustainably. A realistic, evidence-based plan with no crash diets.
Average Baby Weight in Kg and Lbs: Newborn Weight Chart
An average newborn weighs about 7.5 lb (3.3 kg). A full baby weight chart by month in kg and lbs, plus how to read percentiles.
Ideal Weight: Why It Is a Range, Not One Number
There is no single ideal weight. A healthy weight is a range, and chasing one number on the scale is the wrong goal.
Kg to Lbs Cheat Sheet: Gym Plates, Luggage, and Recipes
1 kg is 2.2 lb. A quick kg-to-lbs cheat sheet for gym plates, airline luggage, body weight, and recipes.
How to Convert Kg to Lbs in Your Head (3 Easy Tricks)
Convert kg to lbs in your head: double the kilograms and add 10 percent. Three easy tricks with worked examples.
Airline Luggage Limits Explained: 20kg, 23kg, 32kg in Pounds
The economy checked-bag limit is 23 kg (about 50 lb). Every airline weight limit in kg and pounds, plus how to dodge overweight fees.
What Is 170 cm in Feet and Inches? Height Conversion Guide
170 cm is 5 feet 7 inches. A full height conversion table from 150 to 190 cm, plus the simple conversion math.
How to Measure Your Height Accurately at Home
Measure your height at home with the wall-and-flat-object method. Step-by-step instructions and the common mistakes to avoid.
Cm to Inches Cheat Sheet for Furniture, Screens, and Frames
1 cm is 0.3937 inches. A quick cm-to-inches cheat sheet for furniture, TV screens, picture frames, and paper sizes.
The Ideal Blog Post Length for SEO in 2026
There is no magic word count. The right blog post length is the one that fully answers the search intent, usually 1,400 to 2,500 words.
Character Limits Cheat Sheet: SEO Titles, Meta, and Social
An SEO title should be 50 to 60 characters and a meta description 150 to 160. Every SEO and social media character limit in one table.
Celsius to Fahrenheit Formula: How to Convert (With Tricks)
To convert Celsius to Fahrenheit, multiply by 1.8 and add 32. The formula, a mental-math trick, and a reference table.
Convert Lbs to Kg in Your Head: Fast Mental Math
Convert pounds to kilograms in your head: halve the pounds, then subtract 10 percent. Worked examples and an accuracy table.
Average Weight for Men and Women by Age
The average US man weighs about 199 lb and the average woman about 172 lb. A by-age table, and why average is not a healthy target.
How Do Exchange Rates Work? A Beginner’s Guide
An exchange rate is the value of one currency in another, set by supply and demand. Floating vs fixed rates and what moves them.
The Cheapest Way to Exchange Currency for Travel
The cheapest currency exchange is your bank before the trip and an in-network ATM abroad. Never the airport. A full cost comparison.
What Is Loan Amortization? How It Works, With a Real Example
Loan amortization is paying off a loan with regular equal payments. How it works, with a worked example and a sample schedule.
How to Calculate Loan Payments: The PMT Formula Explained
Calculate any loan payment with the PMT formula. The formula explained step by step, with a full worked example.
What Credit Score Do You Need for a Personal Loan?
You generally need a credit score of about 580 to qualify for a personal loan, and the high 600s or more for good rates.
Biological Age vs Chronological Age: What Is the Difference?
Chronological age is the years since you were born. Biological age is how your body is really aging, and the two can differ.
The Age Gap Rule: Does Half Your Age Plus Seven Hold Up?
The age gap rule says the youngest partner you should date is half your age plus seven. Does it actually hold up?
How to Convert Km/h to Mph (and Pace for Runners)
To convert km/h to mph, multiply by 0.6214. A speed conversion table, a mental-math shortcut, and pace for runners.
What Does My BMI Result Actually Mean?
Your BMI result is a screening flag, not a diagnosis. What each BMI category means for you and what to do next.
BMI by Age: How Healthy Weight Changes Through Life
For adults the healthy BMI range is 18.5 to 24.9 at every age. Children use percentiles, and older adults need extra context.
Why the US Uses Pounds and the World Uses Kilograms
The US uses pounds because it inherited English units at independence and never mandated metric. The full history.
Picture Frame Sizes: Cm to Inches Conversion Guide
Standard picture frame sizes in inches and centimeters, from 4x6 to 24x36, plus how matting works and how to pick a size.