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Fitness & Weight
Calorie Deficit Calculator — Daily Target, Deficit & Timeline
Turn a goal weight and a weekly pace into a clear daily calorie number
A calorie deficit is the gap between the calories you burn in a day and the calories you eat. When you eat fewer calories than you burn, your body makes up the difference by tapping into stored energy — and over time that's how weight comes off. This calculator turns the goal into a single number you can actually use: a daily calorie target.
The math rests on one well-known rule of thumb: 1 pound of body fat holds roughly 3,500 calories. So to lose 1 lb per week you need a deficit of about 3,500 ÷ 7 = 500 calories per day. Want to lose 2 lb per week? That's a 1,000 cal/day deficit. The formula is simple:
Daily target = maintenance calories − (weekly loss in lb × 3,500 ÷ 7).
Worked example: Say your maintenance (TDEE) is 2,400 calories/day and you want to lose 1.5 lb per week. Your deficit is 1.5 × 3,500 ÷ 7 = 750 cal/day, so your daily target is 2,400 − 750 = 1,650 calories/day. If your goal is to drop 20 lb, the timeline is 20 ÷ 1.5 ≈ 13–14 weeks.
Don't know your maintenance number? Enter your age, sex, height (ft + in), weight (lbs) and activity level and the calculator estimates your TDEE using the Mifflin-St Jeor equation, then builds the target from there.
The common mistake: chasing the biggest possible deficit. Cutting to 1,000+ calories below maintenance feels productive, but very low intake is hard to sustain, can cost you muscle, and often backfires with rebound eating. A widely used floor is no fewer than ~1,200 cal/day for women and ~1,500 for men, and a pace of 0.5–2 lb per week for most people. Slower is usually more sustainable.
Also remember the 3,500-calorie rule is an estimate. Real weight loss isn't perfectly linear — water weight, sodium, hormones, sleep, and a slowing metabolism as you get lighter all shift the curve. Use the number as a starting point and adjust based on what the scale actually does over 2–3 weeks.
This tool is informational only and not medical or nutritional advice. Talk with a doctor or registered dietitian before starting any aggressive diet, especially if you have a health condition.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• 1 lb of fat ≈ 3,500 calories • Daily deficit = (weekly loss in lb × 3,500) ÷ 7 • Daily calorie target = maintenance (TDEE) − daily deficit • Timeline (weeks) = pounds to lose ÷ weekly loss rate • TDEE = BMR × activity factor (Mifflin-St Jeor BMR)
📰 Formula
• 1 lb of fat ≈ 3,500 calories • Daily deficit = (weekly loss in lb × 3,500) ÷ 7 • Daily calorie target = maintenance (TDEE) − daily deficit • Timeline (weeks) = pounds to lose ÷ weekly loss rate • TDEE = BMR × activity factor (Mifflin-St Jeor BMR)
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Setting too aggressive a deficit (over 1,000 cal/day) that's hard to sustain.
- Dropping below the safe floor (~1,200 cal/day women, ~1,500 men).
- Treating the 3,500-cal rule as exact — real loss is non-linear week to week.
- Forgetting that maintenance falls as you get lighter, so the deficit shrinks over time.
💡 Tips
- Aim for 0.5–2 lb per week; slower is usually easier to keep off.
- Re-check your TDEE every 10–15 lb lost — your target should drop as you do.
- Pair the deficit with protein and strength training to protect muscle.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/calorie-deficit-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How big a calorie deficit do I need to lose 1 pound a week?
About 500 calories per day. One pound of fat is roughly 3,500 calories, and 3,500 ÷ 7 days = 500 cal/day. For 2 lb/week, you'd need a 1,000 cal/day deficit.
What is a safe calorie deficit?
For most people a 500–750 cal/day deficit (about 0.5–1.5 lb/week) is safe and sustainable. Going beyond 1,000 cal/day, or eating below ~1,200 cal (women) or ~1,500 cal (men), is generally discouraged without medical supervision.
How many calories should I eat to lose weight?
Take your maintenance calories (TDEE) and subtract your daily deficit. If you maintain at 2,200 and want to lose 1 lb/week, eat about 2,200 − 500 = 1,700 calories per day.
What are maintenance calories or TDEE?
TDEE (Total Daily Energy Expenditure) is how many calories you burn in a day, including activity. Eating at your TDEE keeps your weight stable; eating below it creates the deficit that drives weight loss.
Is the 3,500 calories per pound rule accurate?
It's a useful estimate, not an exact law. Real weight loss isn't perfectly linear — water weight, sodium, hormones, and a metabolism that slows as you get lighter all affect the actual rate. Use it as a starting point and adjust to what the scale shows.
How long will it take to lose 20 pounds?
Divide the pounds by your weekly pace. At 1 lb/week, 20 lb takes about 20 weeks; at 1.5 lb/week, roughly 13–14 weeks; at 2 lb/week, about 10 weeks. Faster paces are harder to sustain.
Can I lose weight with diet alone, no exercise?
Yes — weight loss is mainly about the calorie deficit, which you can create through diet. Exercise raises your TDEE (so you can eat a bit more) and helps protect muscle, but the deficit itself is what drives fat loss.
Why did my weight loss stall even though I'm in a deficit?
Plateaus are normal. As you get lighter your maintenance calories drop, so the same intake creates a smaller deficit. Water retention, sodium, and hormones also mask fat loss day to day. Re-check your TDEE and judge progress over 2–3 weeks, not daily.
Is this calculator medical advice?
No. It's an informational estimate using the 3,500-calorie rule and standard formulas. It is not medical or nutritional advice. Talk with a doctor or registered dietitian before starting an aggressive diet, especially with any health condition.