Diet Calculator — Deficit or Surplus

Diet Calculator — Enter Your Details

Choose your goal and pace to get daily calories and a simple macro plan you can follow.

How to Use Diet Calculator — Deficit or Surplus

1. Step 1: Add basics

   Enter age, sex, height, weight, and pick metric or US units.

2. Step 2: Set activity

   Choose your daily activity level to estimate maintenance (TDEE).

3. Step 3: Pick a goal

   Select Lose, Maintain, or Gain and choose plan by weekly rate, % of TDEE, or custom kcal.

4. Step 4: Tune macros

   Adjust the protein (g/kg) and fat (%) sliders; carbs fill the rest automatically.

5. Step 5: Review plan

   Read your target daily calories, weekly change, and suggested macros. Refine pace as needed.

Key Features

• Deficit/surplus presets
• Pace guidance
• Maintenance estimate
• Macro suggestions

Understanding Results

Formula

We estimate your Basal Metabolic Rate (BMR) with the Mifflin–St Jeor equation: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s, where s is +5 for males or −161 for females. Then we multiply BMR by an activity factor to get Total Daily Energy Expenditure (TDEE). Your diet target equals TDEE adjusted by your chosen deficit or surplus. If you plan by weekly rate, we convert that pace using ≈7700 kcal per kilogram (≈3500 kcal per pound) of weight change.

Reference Ranges & Interpretation

For most adults, a 10–25% deficit tends to be sustainable for weight loss, while a 5–15% surplus suits gradual weight gain. Faster rates are possible but often harder to maintain. The weekly change we show is an estimate; short‑term shifts include water and glycogen. Use trends over several weeks to judge progress, and adjust pace if energy, training, or adherence suffer.

Assumptions & Limitations

These numbers are estimates based on population formulas. Individual needs vary with muscle mass, NEAT (spontaneous activity), stress, medications, and health conditions. The 7700‑kcal rule is a useful simplification but not exact for all bodies. This tool is for informational purposes only and isn’t designed for children, pregnancy, or medical nutrition therapy. Re‑estimate as your weight or routine changes.

Complete Guide: Diet Calculator — Deficit or Surplus

Use the diet calculator to choose your target pace and get daily calorie goals with simple guidance for cutting or gaining. Accurate, clear, and easy to use.

This guide shows exactly how to use the diet calculator, how the math works under the hood, and how to set a plan that fits your life. The goal isn’t a rigid rule. It’s a clear starting point you can adjust as your body and routine change.

How the diet calculator works

The diet calculator does three things in a few seconds. First, it estimates your baseline energy need (BMR). Second, it accounts for activity to estimate maintenance (TDEE). Third, it applies your chosen plan—deficit to lose, surplus to gain, or maintenance to hold steady— and outputs daily calories and suggested macros.

You can plan by weekly weight change, by a percent of maintenance, or by a custom daily calorie delta. Weekly rate is intuitive: pick a pace you can live with. Percent is flexible across body sizes. Custom is for experienced users who already know a daily target that tends to work.

If you prefer to double‑check maintenance first, try our Maintenance Calories Calculator for a stand‑alone estimate, or use the integrated activity picker in this tool. For a deep dive into creating a specific deficit, see the Calorie Deficit Calculator.

Picking a deficit or surplus you can keep

The “best” plan is the one you can follow consistently. A large deficit or surplus can look efficient on paper, but real life gets a vote: hunger, training quality, sleep, work stress, and family rhythms all affect adherence. That’s why moderate ranges tend to work well for most people. For weight loss, many do better starting around 10–20% below maintenance, adjusting to 25% only if they feel good and recovery stays solid. For weight gain, a 5–10% surplus is usually enough to progress without adding more fat than you want.

Numbers are helpful; feedback is essential. Track how your body weight trends over 2–4 weeks, then decide whether to keep, slow, or speed up the pace. If you struggle with appetite or recovery, consider smaller changes and keep protein and fiber steady. Our Macro Calculator can help you test different protein/fat splits while keeping calories on target.

Plan by weekly rate vs. % of TDEE vs. custom

You can plan by weekly change (e.g., 0.5 kg/week), by percent of maintenance (e.g., 15%), or by a custom number of calories. The calculator converts weekly rate to calories using a common rule of thumb: roughly 7700 kcal corresponds to 1 kilogram of weight change (≈3500 kcal per pound). This is a simplification—your body will retain or release water along the way—but it’s a helpful guardrail for setting a pace.

Percent of TDEE scales to the person. A 15% deficit for a 3000‑kcal maintenance is 450 kcal, but only 300 kcal if your maintenance is 2000. “Custom kcal” is a direct way to apply what has worked for you before. Whichever method you pick, revisit the numbers as your weight and routine change—maintenance is a moving target.

Estimating maintenance: BMR and activity

Under the hood, the tool uses the Mifflin–St Jeor equation to estimate BMR, then multiplies it by an activity factor to reach TDEE. Mifflin–St Jeor is widely used in clinical and fitness settings and performs well for most adults. Still, two people of the same height and weight can have different needs because of muscle mass and daily movement.

If your job keeps you seated most of the day, start with a lower activity factor and bump it up if your weight drifts lower than planned at the same calorie intake. If you rack up steps or have a physical job, start higher and dial down if you find the target too easy. Maintenance is an estimate you refine in the real world.

To sanity‑check energy balance itself, the NIH offers a helpful overview of calories in vs. out. See the NHLBI guidance on weight control for plain‑language context.

Protein, fat, and carb breakdown

Macros don’t replace calories; they shape them. Protein helps preserve lean mass while dieting, supports muscle gain in a surplus, and tends to keep you full. Fat supports hormones and nutrient absorption. Carbs fuel performance and recovery, particularly around training. Our defaults are a practical middle ground: protein by body weight, a moderate fat percentage, and carbs filling the rest.

If you want to optimize protein for a specific goal, try the Protein Calculator and then return to this page. For general purposes, a range of ~1.2–2.2 g/kg body weight works well for most adults. Endurance athletes or those with higher training volumes may benefit from more carbs; those who prefer a lower‑carb style can set a higher fat percentage and let carbs drop.

How fast should you lose or gain?

Speed is a tradeoff. Faster weight loss can be motivating, but it may be harder to keep up week after week. Slower cuts are easier to live with and often protect training quality. On the gain side, a tiny surplus can feel slow, but it tends to produce steadier strength and muscle with less fat gain.

As a starting point, many people do well with about 0.25–0.75 kg/week for loss, and roughly 0.1–0.25% of body weight per week for gain. If you stall, check sleep, steps, training, and weekend habits before you assume you need a deeper cut or bigger surplus. Consistency over time is what moves the trend line.

Example plans and quick scenarios

Example 1 — Cutting on a busy schedule: You pick 15% below maintenance and set protein around 1.8 g/kg. Training is 3 days per week. After two weeks, weight is down slightly but energy is great, so you keep the same plan. Near week four, progress slows—steps dropped with a hectic work week—so you get walks back to normal first. Only if the 4‑week trend is flat do you nudge calories another 5% lower.

Example 2 — Lean gain for strength: You choose a 10% surplus, keep protein near 1.6–2.0 g/kg, and prioritize consistent sleep. Strength and body weight rise steadily over eight weeks. When the scale jumps faster than expected, you keep calories the same but add a bit more walking to let water and glycogen settle. If trend gain is still high, you trim the surplus to 5–7% for a few weeks.

Example 3 — Returning after a break: You estimate maintenance with the calculator, set a small 10% deficit, and target protein at 1.6–2.0 g/kg. Because you’re rebuilding habits, you give yourself 12 weeks and focus on three anchors: a grocery list with high‑protein staples, a daily step goal you can meet, and consistent bedtime. Slow, boring consistency beats exciting, short‑lived effort.

Adjustments, plateaus, and adherence

Plateaus happen. Before you change numbers, confirm behaviors. It’s normal for a week or two to look flat, especially if training or sodium intake changed. Check your log, steps, and sleep. When you do adjust, change one variable at a time: a small calorie tweak, an extra walk, or a fourth training day. Then give it a week or two.

If you prefer a structured eating window, the Intermittent Fasting Calculator can help you set times that fit your mornings or evenings. If you like a low‑carb or ketogenic style, the Keto Calculator shows targets that keep net carbs low while keeping calories on plan. And if you want to check a simple daily number without macros, try the Calorie Intake Calculator.

Fasting, low‑carb, and other approaches

Many eating styles can work as long as your weekly calorie balance fits your goal. Intermittent fasting, higher‑protein, Mediterranean, plant‑ forward, low‑carb, or low‑fat can all be effective. Pick the one you can keep up. If training performance matters, consider placing more carbs around workouts and keeping protein steady throughout the day.

Research methods and individual physiology differ, which is why real‑ world testing with consistent habits is so valuable. Use the diet calculator to set a clear baseline, then observe: hunger, energy, training quality, sleep, and weight trend. Adjust in small steps. Over a month, those small steps compound.

When to seek professional guidance

If you live with a medical condition, take medications that influence appetite or metabolism, are recovering from injury or illness, or are pregnant or nursing, talk with a qualified clinician or registered dietitian before making significant changes. For a general overview on healthy weight, see the CDC’s healthy weight resources. This site provides tools, not medical advice.

When you’re ready, use the calculator above to set your target. If you want to tune macros further, visit the Macro Calculator, check protein with the Protein Calculator, or verify your base with the Maintenance Calories Calculator.

Frequently Asked Questions