How Many Calories Should I Eat to Lose Weight? Guide & Calculator

Q: How many calories do I need to burn to lose weight?

You don't need to burn calories separately to lose weight — the deficit can come entirely from eating less, entirely from moving more, or a combination of both. The math is simple: 7,700 kcal total deficit equals approximately 1 kg of fat loss.

Q: If I eat 600 calories a day how much weight will I lose?

Eating only 600 kcal a day is a severe restriction not recommended without medical supervision. A more sustainable approach is a 500–600 kcal deficit from your calculated maintenance, not eating 600 kcal total.

Cutting 500–600 calories daily targets roughly half a kilogram of weight loss per week — a rate both the NHS and Mayo Clinic endorse as sustainable for most adults. The real challenge is that “how much should I eat” has no universal answer; it hinges on whether you follow NHS guidance (about 600 kcal daily reduction) or the Mayo Clinic formula (around 500 kcal), and how your age, activity level, and starting weight affect the math.

Safe daily deficit: 500–600 kcal · Female limit for 1lb/week loss: 1,400 kcal · Male limit for loss: 1,900 kcal · Calories per kg fat: 7,700 kcal · NHS weight loss goal: 0.5–1 kg/week

Quick snapshot

1Confirmed facts

500–600 kcal/day deficit is safe for most adults (NHS Better Health)
NHS maintenance: 2,000 kcal/day women, 2,500 kcal/day men (St Catherine’s NHS)
3,500 kcal ≈ 1 pound (0.45 kg) of fat (Mayo Clinic)

2What’s unclear

Exact burn varies significantly by individual metabolism (Mayo Clinic)
Long-term adherence rates for deficit-based plans lack robust data (Mayo Clinic)

3Timeline signal

NHS 12-week plan sets 0.5–1 kg/week as the safe target (NHS Better Health)
Mayo Clinic’s Lose It! phase lasts 2 weeks for initial 6–10 lb loss (Mayo Clinic Diet)

4What’s next

Use a calculator to find your maintenance, then subtract 500–600 kcal
Track intake with NHS-recommended apps like MyFitnessPal

The table below summarises the key figures used throughout this guide.

Label	Value
Standard deficit	500 kcal/day
1 kg fat equivalent	7,700 kcal
Safe weekly loss	0.5–1 kg
10,000 steps burn	300–500 kcal
Female loss limit (NHS)	1,400 kcal/day
Male loss limit (NHS)	1,900 kcal/day
Minimum medically supervised	800 kcal/day
NHS recommended activity	150 min moderate/week

How many calories should I intake a day to lose weight?

Both the NHS and Mayo Clinic anchor their weight-loss advice to the same basic logic: eat fewer calories than your body burns, and you will lose weight. Where they diverge slightly is the recommended deficit size. The NHS recommends reducing daily intake by 600 kcal, while Mayo Clinic guidance points to a 500 kcal daily cut — both leading to roughly 0.5–1 lb (0.25–0.45 kg) of loss per week (Dr Rashid Ali Surgery (NHS-affiliated), Mayo Clinic).

Using a calorie calculator

The most reliable starting point is to calculate your maintenance calories — the amount your body needs to stay at its current weight — then subtract the deficit. Mayo Clinic offers an online calorie calculator that factors in age, gender, height, weight, and activity level to estimate daily needs. For example, Mayo Clinic estimates a 150 lb woman needs roughly 1,500 kcal/day for maintenance without exercise (Mayo Clinic Health System).

Mayo Clinic Calorie Calculator — estimates daily maintenance needs based on activity
Calculator.net — offers BMR (Basal Metabolic Rate) plus activity multiplier
NHS Better Health app — includes 12-week plan with built-in calorie allowance tracker

Factors like age, gender, activity

Age and gender directly affect your basal metabolic rate (BMR) — older adults and women typically have lower BMRs, meaning their maintenance calories are lower. The NHS estimates average maintenance at 2,000 kcal/day for women and 2,500 kcal/day for men (St Catherine’s Surgery (NHS)). Activity level adds another layer: someone with a sedentary job needs fewer calories than someone who walks 10,000 steps daily, which burns an estimated 300–500 kcal depending on body weight.

The implication: a 45-year-old sedentary woman starting at 160 lbs will have a different target than a 25-year-old active man at the same weight — calculators account for this, but fixed “1,200 calorie diets” do not.

The upshot

No single number works for everyone. A calorie calculator that factors in your age, gender, height, weight, and activity level is the only way to get a realistic personal starting point — generic 1,200 kcal rules are a blunt instrument, not a personalized plan.

Is 1200 calories a day ok for losing weight?

WebMD notes that the general minimum for women and those assigned female at birth is 1,200–1,500 kcal per day to avoid unhealthy restriction, while men and those assigned male at birth should stay above 1,500–1,800 kcal (WebMD). Eating below these thresholds without medical supervision can lead to nutrient deficiencies, muscle loss, and a slowdown in metabolism.

For women vs men

The NHS Weight Loss Plan sets 1,400 kcal/day as the upper limit for most women and 1,900 kcal/day for most men when aiming to lose 0.5–1 kg per week (Dr Rashid Ali Surgery (NHS-affiliated)). These figures are already below typical maintenance (2,000 for women, 2,500 for men), reflecting the recommended deficit. Mayo Clinic’s sample meal plan comes in at 1,200 kcal/day, but this is presented as a structured, nutritionally balanced example — not as a universal recommendation (Mayo Clinic Diet).

Risks of very low intake

Very low-calorie diets below 800 kcal/day should only be followed under medical supervision, and even then for a maximum of 12 weeks (MyDiabetesMyWay (NHS Scotland)). Below that threshold, risks include gallstones, electrolyte imbalances, heart arrhythmias, and significant muscle loss — not just fat loss. WebMD advises consulting a doctor before dropping below 1,200 kcal/day (WebMD).

The catch: 1,200 kcal might be perfectly fine for a small, sedentary woman but dangerously low for an active man — the number alone tells you nothing without context.

The catch

Eating 1,200 kcal a day is not automatically “safe for weight loss.” For an active adult or anyone over a certain body weight, it can trigger metabolic slowdown, muscle loss, and nutrient gaps. The threshold that matters is your personal maintenance minus 500–600 kcal — not a generic floor.

Why am I not losing weight on a calorie deficit?

Plateauing despite what appears to be a deficit is one of the most common frustrations in weight loss, and it usually has one of three causes: inaccurate tracking, metabolic adaptation, or hidden calories (WebMD).

Metabolic adaptation

As you lose weight, your body becomes more efficient — it requires fewer calories to sustain a smaller body. A person who started at 180 lbs burning 2,500 kcal/day may only need 2,100 kcal at 160 lbs to maintain. If they keep eating 1,900 kcal (once a 600 kcal deficit), the deficit has shrunk to just 200 kcal, slowing progress to a crawl (Mayo Clinic).

Hidden calories, inaccurate tracking

Studies consistently show that people underestimate caloric intake by 20–50% when self-reporting, especially with “healthy” foods like salads, granola bars, and smoothies that carry more calories than expected. Cooking oils, sauces, and beverages are frequent culprits. Mayo Clinic notes that non-exercise activity thermogenesis (NEAT) — the calories burned moving throughout the day outside formal exercise — can vary by 100–800 kcal/day between individuals, meaning two people eating the same meals can have very different outcomes (Mayo Clinic).

What this means: if you’re stuck, re-estimate your maintenance calories with your current weight, check your portion sizes with a food scale, and consider whether your activity level has dropped as you lost weight.

How many kcal to lose 1 kg?

The foundational number comes from the traditional view that 3,500 kcal equals approximately 1 pound (0.45 kg) of body fat — a figure confirmed by the Mayo Clinic (Mayo Clinic) and supported by NHS Golden Jubilee documentation (NHS Golden Jubilee PDF). That means 7,700 kcal total deficit equals roughly 1 kg of fat.

Basic formula

To lose 1 kg per week, you need a daily deficit of about 1,100 kcal — which is aggressive and typically not sustainable without medical supervision. A more conservative target of 0.5 kg/week requires about 550 kcal/day deficit, close to the 500–600 kcal range recommended by NHS and Mayo Clinic combined (ESHT NHS).

Real-world adjustments

The 3,500 kcal figure is a simplification. As body weight drops, metabolic rate drops with it, meaning the required deficit shrinks over time. Water retention fluctuations of 1–2 kg can mask fat loss on the scale, and glycogen replenishment after exercise can temporarily add water weight. Mayo Clinic notes that the 3,500 kcal rule “is not exact for everyone due to metabolic changes” (Mayo Clinic).

The pattern: the math works on paper, but your body is a moving target. Recalculate your maintenance every 4–6 weeks as weight changes to keep the deficit meaningful.

How many calories should I eat a day by age to lose weight?

Age affects weight loss through two mechanisms: BMR declines roughly 1–2% per decade after age 20, and activity levels tend to decrease. A 20-year-old and a 50-year-old at the same weight and height will have meaningfully different calorie needs.

Teens vs adults

The NHS recommends 150 minutes of moderate activity or 75 minutes of vigorous activity per week for adults aged 19–65 (St Catherine’s Surgery (NHS)). For teenagers, growth is still occurring, and restricting calories too aggressively can interfere with development. Most guidelines suggest teenagers should not go below 1,600–1,800 kcal without medical advice. The focus for teens should be on activity and food quality rather than aggressive calorie restriction.

Calculator tweaks by age

Most calorie calculators (including Mayo Clinic’s) ask for your age and adjust BMR accordingly using the Mifflin-St Jeor equation or similar. For adults over 60, some calculators add a multiplier because muscle mass — and thus BMR — tends to decline with sarcopenia. The NHS Digital Weight Management Programme sets eligibility at BMI ≥ 30 (or ≥ 27.5 for Black, Asian, and minority ethnic groups), with a focus on sustained habit change rather than rapid restriction (NHS England).

The trade-off: older adults have less room for error in deficits — the same 600 kcal cut that works for a 25-year-old may be too aggressive for a 65-year-old with a lower BMR and reduced activity tolerance.

Why this matters

A 50-year-old woman who was eating 2,000 kcal to maintain her weight at 35 now maintains at roughly 1,850 kcal. If she drops to 1,400 kcal without recalculating, she is running a 450 kcal deficit — not the 600 kcal she thinks. Recalculate every 4–6 weeks as weight and age adjust your baseline.

Steps: How to count calories for weight loss

Find your maintenance number. Use the Mayo Clinic Calorie Calculator or the NHS Better Health app to estimate how many calories your body needs to stay at its current weight. Input your age, gender, height, weight, and activity level honestly.
Subtract 500–600 kcal. NHS guidance recommends a 600 kcal reduction; Mayo Clinic points to 500 kcal. Either works — the difference is marginal (roughly 0.05 kg/week). Pick one and stay consistent.
Track intake accurately. Use a food scale and an app like MyFitnessPal or the NHS Weight Loss Plan app. Log everything — including cooking oils, drinks, and “healthy” snacks. Studies show that accurate tracking is where most people fall short.
Weigh yourself weekly, not daily. Daily weight fluctuations from water retention can mislead. Weight yourself once a week at the same time, in the same state, and track the trend over 4 weeks.
Add activity to amplify the deficit. NHS recommends 150 minutes of moderate activity per week. If your goal is faster loss, add steps — 10,000 steps burns an estimated 300–500 kcal depending on body weight and pace.
Recalculate every 4–6 weeks. As you lose weight, your maintenance calories drop. If you keep eating the same number, your deficit shrinks and progress stalls. Use a calculator again with your new weight to update your target.
Know when to seek help. If you’ve been in a consistent deficit for 8+ weeks with no weight change, or if you feel fatigued, hair-thinning, or consistently cold, consult a doctor or registered dietitian.

Upsides

500–600 kcal deficit is well-supported by NHS and Mayo Clinic for sustainable 0.5–1 kg/week loss
Structured programs like NHS 12-week plan and Mayo Clinic Diet provide meal plans and tracking tools
No special foods or products required — works with any diet pattern

Downsides

Tracking accurately is time-consuming and prone to human error
Metabolic adaptation reduces deficit effectiveness over time
Very low-calorie diets carry medical risks without supervision

What experts say

“A good rule of thumb for healthy weight loss is a deficit of about 500 calories per day. That should put you on course to lose about 1 pound per week.”

— WebMD (Health Publisher)

“To lose weight, the average person should reduce their daily calorie intake by 600 kcal.”

— NHS via Dr Rashid Ali Surgery (NHS-affiliated Clinic)

“In general, if you cut about 500 calories a day from your usual diet, you may lose about ½ to 1 pound a week.”

— Mayo Clinic (Medical Institution)

Bottom line: A 500–600 kcal daily deficit is the evidence-backed sweet spot for most adults — backed by both NHS and Mayo Clinic — yielding 0.5–1 kg/week safely. Women should not typically drop below 1,400 kcal/day and men below 1,900 kcal/day without professional guidance. For anyone tracking their intake: use a calculator to find your current maintenance, then subtract the deficit. Recalculate every few weeks as your weight changes. Those who stall despite an apparent deficit almost always need to re-estimate their maintenance number, not simply eat less.

Related reading: water retention · nutrition facts

Additional sources

mayoclinic.org, mayoclinic.org

NHS and Mayo Clinic advocate a 500-600 kcal daily deficit for safe loss, with tools like the safe deficit guide tailoring targets to your age, gender and activity.

Frequently asked questions

How many calories should a woman eat to lose weight?

The NHS sets 1,400 kcal/day as the upper limit for most women aiming for 0.5–1 kg/week loss, based on a 600 kcal deficit from an average maintenance of 2,000 kcal. Mayo Clinic’s 500 kcal deficit model points to roughly 1,500 kcal/day for the same loss rate. The exact number depends on age, height, current weight, and activity level — a calculator is the only reliable way to personalise it.

How many calories do I need to burn to lose weight?

You don’t need to “burn” calories separately to lose weight — the deficit can come entirely from eating less, entirely from moving more, or a combination of both. The math is simple: 7,700 kcal total deficit equals approximately 1 kg of fat loss. A 500–600 kcal daily deficit (from food alone, activity alone, or both) achieves that target over a week.

How many calories should a teenager eat to lose weight?

Teenagers should not follow aggressive calorie restriction without medical supervision. Most guidance suggests a minimum of 1,600–1,800 kcal/day for teens, with the focus on nutrient density and physical activity rather than cutting calories sharply. The better approach for teens is increasing activity and improving food quality — restricting during a growth period carries developmental risks.

How many calories do 10,000 steps burn?

Walking 10,000 steps burns an estimated 300–500 kcal, depending on body weight, walking speed, and terrain. A lighter person at a moderate pace burns closer to 300 kcal; a heavier person or faster pace can approach 500 kcal. Adding 10,000 steps to your daily routine effectively amplifies any calorie deficit you’re running from diet alone.

Does fasting from 7pm to 7am work?

Time-restricted eating windows like 7 pm to 7 am can help some people reduce overall calorie intake by limiting late-night snacking — the period when people are most likely to consume calories without compensating during the day. However, it is not magic: if total daily calories still exceed maintenance, weight loss will not occur. The timing of eating has less impact than the total amount.

If I eat 600 calories a day how much weight will I lose?

Eating only 600 kcal a day is a severe restriction classified as a very low-calorie diet (VLCD). Without medical supervision, this is not recommended. With a 600 kcal intake versus a maintenance of, say, 2,000 kcal, the deficit would be 1,400 kcal/day — theoretically over 2 lbs (0.9 kg) of fat per week. However, such a large deficit triggers metabolic slowdown, muscle loss, and nutritional deficiencies. A more sustainable approach is a 500–600 kcal deficit from your calculated maintenance, not eating 600 kcal total.