Free tool
Calorie intake calculator
A free daily calorie calculator showing estimated maintenance plus a conservative starting range for losing, maintaining, or gaining, with every assumption printed.
Fill in your measurements, activity level, and goal to see a starting range. Nothing you type here leaves your browser.
A starting estimate to adjust from, not a prescription. Nothing you enter is sent anywhere or stored.
How it is built
Three steps, then the evidence
Rather than handing back a single figure with no working, the calculator prints each stage so you can see which assumption is doing the work.
- 01
Resting energy
Mifflin–St Jeor predicts what you burn at complete rest from height, weight, age, and sex.
- 02
Daily expenditure
That figure is multiplied by a physical activity band from the IOM Dietary Reference Intakes. The result is your estimated maintenance.
- 03
A starting range
10–20% below maintenance to lose, 5–12% above to gain. A percentage, not a flat number of calories.
- 04
Then evidence
Live on it for two or three weeks. The scale and how you feel tell you whether the estimate was close.
Why a percentage
A flat 500-calorie deficit is not the same deficit for everybody
It is mild for a 100 kg man and aggressive for a 50 kg woman. Expressing the adjustment as a percentage of maintenance is how the same guidance scales with body size. It is also why most calculators produce targets that are too low for the people least able to afford them.
The floor
The low end stops
No loss target below roughly 1,200 kcal for women or 1,500 for men. Below that, intake belongs with a professional. If the percentage would have gone lower, the calculator says so.
The timeline
A first approximation, not a date
Give it a goal weight and it estimates how long that might take, using the rule that a kilogram of body weight is worth about 7,700 kcal. That rule is wrong in a predictable direction: it assumes your expenditure stays where it started. It does not, so weight loss slows and the linear estimate runs optimistic over months.
- Shown as a rough duration, never as a date
- The assumption is printed next to the number
- Points at the NIDDK Body Weight Planner for a model that adapts
Where it declines to answer
Questions arithmetic should not be answering
In these cases the calculator withholds a number rather than producing a confident-looking one, and points at someone qualified instead.
- Under twenty, energy needs during growth are assessed against age- and sex-specific references, not adult equations.
- During pregnancy and breastfeeding, requirements are higher and change by stage.
- For anyone with a difficult relationship with food, a calorie target can make it worse.
- Past the validated measurement ranges, the equation is being extrapolated rather than applied.
For coaches
The starting number matters less than what you do next
A hypothesis, not a prescription. It only works if the target and the evidence sit in the same place.
- Targets in the client's record
- Beside the meals you built for them.
- Logged against the same library
- Plan and reality in the same units.
- Check-ins that show the change
- So an adjustment rests on what actually happened.
Limits
What this does not tell you
- Every part of it is an estimate stacked on an estimate: a predicted resting rate, multiplied by a broad activity band, adjusted by a percentage.
- It assumes your expenditure holds steady. It does not. As weight comes off, so does the energy cost of carrying and moving it, which is why real weight loss slows down.
- It says nothing about what the calories are made of. Protein, fibre, and meal timing all change how a given intake feels to live on.
- Logged intake is systematically under-reported, often by a wide margin, so the gap between a plan and reality is usually larger than people expect.
- It cannot account for medications, thyroid conditions, or a long dieting history, all of which move the real number.
Sources
- Mifflin MD et al. (1990) — A new predictive equation for resting energy expenditure in healthy individuals
- NCBI Endotext — Estimating energy requirements
- Institute of Medicine — Dietary Reference Intakes for energy and macronutrients
- NIDDK — Body Weight Planner
- Ages supported
- adults aged 20 and over, outside pregnancy and breastfeeding
- Formulas and sources last reviewed
Keep reading
- BMR calculatorEstimate resting energy expenditure with Mifflin–St Jeor, and see the difference between that and what you burn in a day.
- BMI calculatorWork out an adult BMI in metric or imperial, with the category and the healthy weight range for your height.
- NutritionMeal options that all hit the same targets, switched on per client, logged against a 300,000-food library.
- Check-insBuild the form once, schedule it, and get each response back with the changes laid out and a draft reply to edit.
A number is a start. Coaching is the rest.
Straton keeps a client's targets, their logs, and their check-ins in one record, so an estimate turns into something you can adjust week to week.