BMI Calculator

Calculate your Body Mass Index (BMI) in metric or imperial units and see whether you're underweight, normal, overweight, or obese. Free, instant, no signup.

Formula: BMI = weight (kg) ÷ height² (m) | Imperial: BMI = 703 × lb ÷ in²

How to use the BMI Calculator

  1. Enter your values. Fill in the fields with your numbers.
  2. Calculate. Press Calculate to run the bmi calculator.
  3. Use the result. Copy the result or try a related tool next.

Why use our BMI Calculator

Instant results. Enter your figures and the bmi calculator returns an answer in seconds.
Free & private. Runs in your browser — no signup, and nothing is sent to a server.
Accurate. Uses standard formulas so you can rely on the numbers.

Free to use — premium coming soon

FREE
  • Unlimited calculations
  • Instant results
  • No signup
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  • Save & compare scenarios
  • Export results

About the BMI Calculator

The BMI Calculator turns your height and weight into a single number, your Body Mass Index, and then tells you which standard weight category that number falls into. BMI is defined as your weight in kilograms divided by the square of your height in metres (kg/m2); if you enter imperial units, the tool applies the equivalent formula of weight in pounds times 703, divided by height in inches squared. The result is a quick, widely-used screening figure that doctors, insurers and fitness apps reference, which makes it a handy starting point when you want to see roughly where your weight sits.

Reach for this calculator when you want a fast benchmark rather than a clinical diagnosis. It is useful before a doctor's visit, when tracking weight change over months, or when you simply want to understand a BMI figure quoted somewhere else. Enter your height and weight, switch between metric and imperial if needed, and the tool returns both your exact BMI value and its category. The standard adult bands are: underweight below 18.5, healthy weight from 18.5 to under 25, overweight from 25 to under 30, and obesity at 30 or above (which is further split into Class 1, 2 and 3).

Under the hood the calculation is pure arithmetic, so it works the same whether you weigh yourself in the morning or evening. The only thing that changes the answer is the accuracy of your inputs, so use a recent, reliable height and weight. Because BMI relies on just two measurements, it deliberately ignores body composition: it cannot tell muscle from fat, and it does not account for bone density, sex differences or where fat is stored. A very muscular athlete and a sedentary person can share the same BMI while having completely different body fat levels.

Treat your result as a screening signal, not a verdict. Health authorities such as the CDC describe BMI as one indicator to consider alongside other factors, not a diagnosis, and recommend discussing your number with a healthcare provider. This tool runs entirely in your browser, so the height and weight you type are used only to compute your result on your own device and are not sent to a server or stored. That means you can check your BMI privately, as many times as you like, without creating an account or sharing any personal health data.

Frequently asked questions

How is BMI actually calculated?

BMI is your weight in kilograms divided by your height in metres squared (kg/m2). In imperial units, multiply your weight in pounds by 703, then divide by your height in inches squared. This calculator applies whichever formula matches the units you choose.

What is a healthy BMI range for adults?

For adults aged 20 and over, a BMI from 18.5 to just under 25 is classed as a healthy weight. Below 18.5 is underweight, 25 to under 30 is overweight, and 30 or above falls into the obesity range.

Is BMI accurate for athletes and very muscular people?

Not always. BMI cannot distinguish muscle from fat, and muscle is roughly 15% denser than fat, so muscular athletes often show a high BMI despite low body fat. For them, body fat percentage or waist measurements give a clearer picture.

Can I use this calculator for children or teenagers?

No. This tool uses the adult formula. Children and teens are still growing, so their BMI must be read as a percentile for their exact age and sex using a dedicated child-and-teen BMI chart instead.

Does the calculator save or send my height and weight?

No. The calculation happens entirely in your browser on your own device. Your measurements are not uploaded to a server, stored, or linked to any account, so you can check your BMI completely privately.

From our blog

How to Find Your Break-Even Point and Use It to Make Better Decisions

By the Super Simple Digital Tools Team · Updated June 2026

Most businesses fail not because nobody buys, but because they never knew how much they had to sell to cover their costs. The break-even point answers that question directly: it is the sales volume at which total revenue equals total cost, so you are neither losing money nor making it. Everything above that line is profit, and everything below it is a loss you are funding out of pocket. Knowing the exact number turns vague optimism into a concrete target you can manage against.

Start by sorting your costs into two buckets. Fixed costs are the bills that arrive whether you sell one item or a thousand: rent, salaried staff, insurance, accounting software, and loan payments. Variable costs are tied to each sale: the materials in the product, packaging, shipping, hourly labor for that order, and the cut a payment processor takes. The cleaner this split, the more trustworthy your result, so it is worth scanning a few months of statements and assigning every line to one bucket before you calculate anything.

Next, find the contribution margin, the engine of the whole calculation. Subtract the variable cost per unit from the selling price; what remains is the money each sale contributes toward fixed costs. Divide your total fixed costs by that per-unit margin and you get the number of units you must sell to break even. To express the same point as revenue, divide fixed costs by the contribution margin ratio (the margin as a percentage of price). A product priced at $50 with $30 of variable cost has a $20 margin and a 40% ratio, so $8,000 of fixed costs breaks even at 400 units or $20,000 in sales.

The real value comes from running scenarios. Drop the price by 10% and watch how many more units you suddenly need to sell; the contribution margin shrinks and the break-even point climbs fast. Negotiate a cheaper supplier and the margin widens, pulling break-even down. This is why the SBA lists smarter pricing and catching hidden expenses among the main benefits of the calculation: it shows the trade-offs before you commit real money. Compare your break-even sales to what you actually expect to sell, and the gap between them is your margin of safety, the cushion before a slow month tips you into a loss.

Finally, keep the limitations in mind so the number stays honest. The math assumes price, variable cost, and fixed costs hold steady across the volume you are projecting, but bulk discounts, overtime, and tiered pricing can bend those lines in the real world. Recalculate whenever a major cost or price changes, and pad your fixed costs slightly to absorb surprises. Used this way, break-even analysis becomes a recurring health check rather than a one-time spreadsheet exercise, guiding pricing, launches, and growth decisions with facts instead of guesswork.

  • Sort every expense into fixed or variable before you start; misclassifying even one recurring cost can swing your break-even point significantly.
  • Include payment-processing fees and shipping as variable costs, since they scale with each sale and quietly eat into your contribution margin.
  • Run at least three scenarios, current price, a discount, and a premium, to see which lever lowers your break-even point with the least effort.
  • After finding break-even, subtract it from your realistic sales forecast to get your margin of safety, the buffer you have before a slow period creates a loss.

Read the full guide →

Tool by the Super Simple Digital Tools Team. Reviewed by our editorial team. Free to use, no signup required.

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