Direct Answer
To lose 0.5-1 lb/week, eat 300-500 calories below TDEE daily. A moderately active 40-year-old woman (TDEE ~1,900) might target 1,400-1,600 calories; a man at TDEE ~2,600 might target 2,100-2,300.
Use the Calorie Deficit Calculator for your age, weight, height, and activity.
Last verified on: June 28, 2026
Editorial note: Health calculators provide general estimates — not medical diagnosis or personalized nutrition or treatment advice. Consult a physician or registered dietitian for individual guidance.
Research method: Daily Calcs reviewed CDC, NIH, and peer-reviewed clinical guidelines and validated calculator formulas on June 28, 2026.
Calorie Targets by Activity (170 lb woman, age 35)
| Activity level | Est. TDEE | Weight-loss target (−500) |
|---|---|---|
| Sedentary | 1,740 | 1,240 |
| Moderate | 2,030 | 1,530 |
| Very active | 2,320 | 1,820 |
Safe Deficit Guidelines
| Goal | Weekly loss | Daily deficit |
|---|---|---|
| Moderate | 0.5 lb | ~250 cal |
| Standard | 1 lb | ~500 cal |
| Aggressive (short-term) | 1.5 lb | ~750 cal |
Why Age and Activity Change Your Calorie Target
Total daily energy expenditure (TDEE) is not one number for life. Basal metabolic rate (BMR) — calories burned at rest — falls roughly 2% to 3% per decade after age 20 because muscle mass typically declines without resistance training. Activity multipliers widen the gap further: a sedentary desk worker might multiply BMR by 1.2, while a construction worker or daily runner might reach 1.75.
The CDC recommends gradual loss of 1 to 2 pounds per week for most adults. That maps to a 500 to 1,000 calorie daily deficit from maintenance — but smaller deficits are easier to sustain and preserve lean mass, especially after 40.
Worked Example: 45-Year-Old Woman, 170 lb, Moderate Activity
Assume:
- sex: female
- age: 45
- weight: 170 lb
- height: 5’6”
- activity: moderate (3 to 4 workouts per week)
Using Mifflin-St Jeor:
- BMR ≈ 1,420 calories
- TDEE at moderate activity (×1.55) ≈ 2,200 calories
- weight-loss target at −500 deficit ≈ 1,700 calories
At 1,700 calories with 140g protein (560 cal), she preserves muscle better than at 1,200 calories with low protein. Expected loss: ~1 lb/week if intake matches the estimate.
After losing 15 pounds, TDEE drops to roughly 2,050 — she should recalculate rather than stay at 1,700 indefinitely.
Calorie Target by Age (Same Weight, Moderate Activity)
| Age | Est. BMR (170 lb woman) | Est. TDEE | Loss target (−500) |
|---|---|---|---|
| 25 | 1,530 | 2,370 | 1,870 |
| 35 | 1,480 | 2,290 | 1,790 |
| 45 | 1,420 | 2,200 | 1,700 |
| 55 | 1,360 | 2,110 | 1,610 |
What to Do Next With Your Number
- Run the calculator with honest activity level — most people overestimate.
- Set protein first at 1.6 to 2.0 g/kg target body weight before cutting carbs or fat.
- Track weight 2 to 4 weeks on the same intake; adjust by 100 to 150 calories if loss is too fast or slow.
- Recalculate every 10 to 15 pounds lost or when activity changes materially.
- Stop or slow the deficit if fatigue, hair loss, or menstrual changes appear — consult a clinician.
Weight-Loss Planning Checklist
- Calculate TDEE with current weight and activity level
- Subtract 300 to 500 calories for moderate loss
- Set protein at 25% to 35% of calories
- Weigh daily; use weekly average trend
- Recalculate after 10 to 15 lb loss
Common Mistakes When Cutting Calories
Cutting too aggressively is the most frequent error. Deficits above 750 calories daily often trigger muscle loss, fatigue, and rebound eating. Older adults who slash to 1,200 calories without adequate protein lose lean mass faster — compounding the age-related metabolic decline.
Another mistake is eating back all exercise calories. Fitness trackers overestimate burn by 20% to 40%. If your TDEE calculator already includes activity, treat workout calories as already counted unless weight trends show you are losing too fast.
Finally, never use arbitrary 1,200-calorie floors without checking math. A 5’10” active man with 2,400 TDEE needs 1,900+ calories for a moderate deficit — not 1,200.
Assumptions and Limitations
This guide uses Mifflin-St Jeor BMR and standard activity multipliers. Actual metabolism varies with genetics, thyroid function, medications, and sleep quality. Pregnancy, breastfeeding, eating disorders, and chronic illness require clinician-guided targets — not calculator output alone.
Calorie labels and portion estimates carry 10% to 20% error. Weighing food for two weeks calibrates eyeball portions better than switching diets repeatedly.
What This Means for Your Personal Numbers
Generic examples help you understand the logic — your outcome depends on inputs only you know. Run the related calculator with your age, weight, income, loan amount, or location before treating any table row as a target. Adjust one variable at a time so you can see which lever moves the result most.
If the calculator output surprises you, verify assumptions first: activity level, tax district, insurance quote, cycle length, or credit tier. Small input changes often move results more than rounding differences between published benchmarks and your situation.
When numbers still look wrong after honest inputs, use 2 to 4 weeks of tracking — weight trend, home readings, spending log, or rate quotes — to calibrate. Calculators start the conversation; your data confirms it.
Calculator Methodology
The Calorie Deficit Calculator estimates BMR (Mifflin-St Jeor), multiplies by activity factor for TDEE, and subtracts your chosen deficit for a daily calorie target.
Assumptions: You enter sex, age, weight, height, activity, and goal.
Limitations: Not medical nutrition therapy — thyroid, medications, and pregnancy require clinician guidance.
Related Reading
- TDEE Calculator Results Guide — interpret your burn rate
- Macro Split for Weight Loss vs Muscle Gain — protein and carb targets
- Calorie Deficit Calculator — personalized target
Official and Supporting Sources
Next Step
Get your daily calorie target with the Calorie Deficit Calculator.
Frequently Asked Questions
How many calories should I eat to lose weight?
Eat 300 to 500 calories below your TDEE (total daily energy expenditure) to lose about 0.5 to 1 pound per week. A woman with 1,900 TDEE might target 1,400 to 1,600 calories; a man at 2,600 TDEE might target 2,100 to 2,300. Deficits above 1,000 calories risk muscle loss and are hard to sustain. Recalculate every 10 to 15 pounds lost because TDEE drops with weight.
How does age affect calories needed for weight loss?
TDEE falls 2% to 3% per decade after 20 due to lower muscle mass and activity — a 50-year-old burns 150 to 300 fewer calories than at 25 at the same weight. Post-menopausal women often see another 100 to 200 calorie drop. Older adults should prioritize protein (1.6 to 2.2 g/kg) and resistance training to preserve muscle while in deficit.
How do activity levels change calorie targets?
Sedentary TDEE might be 1.4x BMR; very active can reach 1.9x BMR. A 170-pound woman with BMR 1,450 burns ~2,030 at moderate activity but only ~1,740 if sedentary — a 290 calorie swing. Do not eat exercise calories back unless hunger signals require it — trackers overestimate burn 20% to 40%.
Is 1,200 calories safe for weight loss?
1,200 calories is a common floor for women but may be too low for taller or active women — nutrient deficiencies and fatigue follow. Men generally should not go below 1,500 without medical supervision. If 1,200 is above your TDEE minus 500, use the higher deficit target instead of arbitrary floors.
Calorie counting vs intermittent fasting: Which works better?
Both work when they create the same deficit — weight loss follows energy balance, not meal timing alone. Intermittent fasting helps some people eat less without tracking. Calorie counting gives precision for plateau debugging. Choose the method you sustain 6+ months; adherence beats protocol for most adults.
How fast should I lose weight safely?
CDC and major clinical guidelines suggest 1 to 2 pounds per week for most adults — faster loss is common early (water) but should slow. At 250+ pounds, 2 pounds weekly is often achievable; at 150 pounds, 0.5 to 1 pound is more realistic. Plateaus after 4 to 6 weeks mean recalculating TDEE, not slashing calories further immediately.
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