Transparent calculator · Energy 1.0
Maintenance & Energy Needs Calculator
Estimate resting energy and a deliberately broad maintenance range, with an optional 14-day reality check.
Purpose
What this tool is for
Use this when you need a transparent starting range for everyday energy intake—not a target-date diet prescription.
Audience
Who it is for
Generally healthy adults aged 19–78 who train recreationally and understand that an equation is only a starting estimate.
Input glossary
What each field means
| Input | Unit or choice | Why it matters |
|---|---|---|
| Age | years | The equation subtracts five kilocalories for each year of age. |
| Weight | kg or lb | Converted to kilograms before it enters the equation. |
| Height | cm or ft/in | Converted to centimetres before calculation. |
| Equation branch | female / male | Mifflin–St Jeor published two constants. This is an equation parameter, not a complete description of sex or gender. |
| Activity band | light / moderate / vigorous | Selects a broad FAO physical-activity-level band; it is not a wearable measurement. |
| Optional log | 14 weights + 14 intake values | Compares two seven-day weight averages and reports logged intake only when the trend is broadly stable. |
Method · Energy 1.0
The formula or decision logic
Resting energy estimate = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + equation constant. The constant is +5 for the published male branch and −161 for the published female branch.
The estimate is multiplied by a broad physical-activity-level range: light 1.40–1.69, moderate 1.70–1.99 or vigorous 2.00–2.40.
For the optional log, the mean of days 8–14 is compared with days 1–7. A trend within ±0.25% per week is labelled “broadly stable”; that band is a Nutrinaut planning heuristic, not a clinical threshold.
References support the method or context; they do not validate an individual result. See the sources.
Worked example
Example, not a recommendation: Sam’s starting range
- Sam uses the male equation branch, is 30 years old, weighs 70 kg and is 175 cm tall.
- 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1,648.75 kcal/day resting estimate.
- Using the light PAL band: 1,648.75 × 1.40–1.69 = 2,308–2,786 kcal/day.
Interactive calculator
Estimate your starting range
Nothing you enter is sent to our server. Calculation happens in this browser.
Limitations
What the result cannot tell you
- Equations can differ materially from measured expenditure.
- Activity bands are coarse and day-to-day needs vary.
- Fluid shifts, menstrual-cycle changes, travel, illness and inconsistent food logging can obscure a two-week trend.
- The tool does not calculate a deficit, surplus, “safe minimum,” weight-loss rate or target date.
Questions specific to this tool
Frequently asked questions
Is maintenance the same every day?
No. Movement, training, recovery and normal measurement error vary. The range is more honest than a single fixed number.
Why does the tool ask for an equation branch?
The published Mifflin–St Jeor equation contains different male and female constants. It did not provide another validated parameterisation.
Is 14 days always enough?
No. Two weeks is a practical observation window, not proof of true energy expenditure. Noisy data or a clear trend means gathering more data is sensible.
Should I add exercise calories again?
Not automatically. The activity multiplier is intended to represent total daily activity. Adding the same exercise again can double-count it.
Why can weight rise without an intake change?
Hydration, glycogen, food mass, sodium, menstrual-cycle changes and measurement timing can all alter scale weight without implying a matching fat change.
Primary and official references
Sources
A new predictive equation for resting energy expenditure in healthy individuals
American Journal of Clinical Nutrition / PubMed · 1990
Supports: Resting-energy equationHuman energy requirements: physical activity level
FAO/WHO/UNU · 2004
Supports: PAL categories and uncertaintyFound a numerical or source issue? Send a correction with the page URL.