Calorie Calculator Widget

Add a daily calorie calculator to your website. Visitors enter their details and activity level and see estimated maintenance calories plus targets for mild or moderate weight loss and gain, with a warning whenever a target falls below a safe minimum.

Health & Fitness Calculator Runs in your browser Free · no ads

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<iframe src="https://a2z.tools/embed/w/calorie-calculator" title="Calorie Calculator by A2Z Tools" width="100%" height="840" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.

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How it works

Resting energy is estimated with the Mifflin-St Jeor equation and multiplied by one of five activity multipliers (1.2 to 1.9), the same method as the A2Z TDEE calculator. Those multipliers are a long-standing convention in fitness calculators rather than the output of one validation study; the FAO/WHO/UNU 2004 report on human energy requirements describes the same idea as physical activity level (PAL). The goal table adds or subtracts 250 and 500 kcal a day and converts the difference into a weekly change with Wishnofsky's 1958 rule of 3,500 kcal per pound (about 7,700 kcal per kg), with a note that real loss slows as the body adapts. Any target under 1,200 kcal for women or 1,500 kcal for men is starred with a warning to seek medical supervision - the floors Harvard Health gives - rather than shown as a plain recommendation.

Calculation method

  • BMR (Mifflin-St Jeor) = 10 x kg + 6.25 x cm - 5 x age + 5 (men) or - 161 (women)
  • Maintenance (TDEE) = BMR x activity factor: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 extra active; rounded to whole kcal
  • Targets = TDEE - 500, - 250, 0, + 250, + 500 kcal a day
  • Weekly change = daily difference x 7 / 7,700 kcal per kg (3,500 kcal per lb, Wishnofsky 1958), shown to 2 decimals in kg or whole lb
  • Targets below 1,200 kcal (women) or 1,500 kcal (men) are starred and trigger a warning

Worked examples

Lightly active woman

Inputs: Female, 30 years, 165 cm, 68 kg, light activity (x 1.375)

Result: Maintenance 1,925 kcal/day (BMR 1,400); lose-weight target 1,425 kcal at about -0.45 kg a week

BMR 680 + 1,031.25 - 150 - 161 = 1,400.25; x 1.375 = 1,925.3. 500 x 7 / 7,700 = 0.45 kg.

An estimate for general information only - not medical advice. Talk to a doctor or registered dietitian about your health.

Limitations

  • The 1.2-1.9 multipliers are a convention without a single validating study; they sit below the FAO/WHO/UNU PAL ranges (1.40 and up) at the sedentary end, so treat the level as a starting guess.
  • The weekly change ignores metabolic adaptation, water shifts and changes in body composition, so real progress usually slows after the first weeks.
  • Not for under-18s, pregnancy, breastfeeding, eating disorders or medically supervised diets.

Where publishers use it

  • Personal trainers and online coaches giving clients a starting calorie figure
  • Healthy-eating blogs and recipe sites that discuss portion sizes and energy balance
  • Gym and leisure-centre websites with a member resources page
  • Weight-loss articles that want a responsible calculator with built-in safety floors

Questions

How accurate is the maintenance figure?

It is an estimate. Both the BMR equation and the activity factors are averages, so real needs can differ by several hundred calories. Tracking weight for a few weeks and adjusting is the practical way to refine it.

Why are some targets marked with an asterisk?

They fall below 1,200 kcal a day for women or 1,500 kcal for men. Harvard Health advises not going below those figures except under the supervision of a health professional, so the widget warns instead of silently recommending them.

Is 500 kcal a day really 0.45 kg a week?

That is Wishnofsky's 1958 rule of 3,500 kcal per pound. Later modelling work has shown it overstates long-term loss, because energy needs fall as weight drops, so treat the weekly figure as a first-month guide only.

Which activity level should visitors pick?

Sedentary for desk work with little exercise, light for exercise one to three days a week, moderate for three to five days, very active for hard exercise six or seven days and extra active for physical jobs plus training. Most people overestimate their level.

Sources

  1. A new predictive equation for resting energy expenditure in healthy individuals (Mifflin, St Jeor et al.) - American Journal of Clinical Nutrition 51(2):241-247, 1990 . Resting energy equation
  2. Human energy requirements - Report of a Joint FAO/WHO/UNU Expert Consultation (chapter 5, PAL) - FAO, Rome 2004 . Physical activity level concept; sedentary/light lifestyles PAL 1.40-1.69
  3. Caloric equivalents of gained or lost weight (Wishnofsky) - American Journal of Clinical Nutrition 6(5):542, 1958 . 3,500 kcal per pound rule
  4. Calorie counting made easy - Harvard Health Publishing . Minimum of 1,200 kcal (women) and 1,500 kcal (men) without professional supervision

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools Calorie Calculator
https://a2z.tools/tdee-calculator

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