Weight Loss Calorie Calculator — Deficit & Goal Date Planner

How this calculator works

The planner uses the long-standing approximation that about 3,500 kcal equals one pound of body weight (about 7,700 kcal per kg):

• By rate: daily deficit = weekly loss × 3,500 ÷ 7; daily target = TDEE − deficit; weeks = amount to lose ÷ weekly loss.
• By goal date: weekly loss needed = amount to lose ÷ weeks available; the deficit and daily target follow from that.

For comparison, the 2013 AHA/ACC/TOS adult obesity guideline suggests a deficit of about 500–750 kcal a day, or intakes of roughly 1,200–1,500 kcal a day for women and 1,500–1,800 kcal a day for men. The planner warns if your target drops below 1,200 (women) or 1,500 (men) kcal, or if the rate is faster than about 1% of body weight a week.

By Suhaib Hassan · Reviewed 28 September 2026 against the AHA/ACC/TOS guideline and CDC guidance · How CalculatePilot verifies formulas →

A worked example

Maintenance of 2,200 kcal, 180 lb now, 160 lb goal, 1 lb a week: deficit = 1 × 3,500 ÷ 7 = 500 kcal, so the target is 1,700 kcal a day, and 20 lb at 1 lb a week takes about 20 weeks. Wanting to finish in 10 weeks would need 2 lb a week — a 1,000 kcal deficit and a 1,200 kcal target, right at the guideline floor for women.

Why the real timeline is usually longer

The 3,500 kcal rule is a useful planning tool, but it overestimates long-term loss: as you get lighter, your maintenance calories fall, so a fixed intake produces a shrinking deficit. Research by Hall and colleagues at the NIH showed weight loss slows over time for this reason. Recalculate every few weeks with an updated TDEE, or use our Calorie Calculator, which projects your weight week by week as maintenance changes.

The CDC notes that people who lose weight gradually and steadily — about 1 to 2 pounds a week — are more likely to keep it off.

Sources

• Jensen MD, Ryan DH, Apovian CM, et al. 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults. Circulation 2014;129(25 Suppl 2):S102–S138.
• Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–837.
• CDC — Losing weight
• NIH Body Weight Planner

Read the guide: How many calories to eat to lose 1 pound a week?

Frequently asked questions

Why 3,500 calories per pound of fat?expand_more

It's a long-standing approximation for the energy stored in a pound of body fat. It works for short-term planning, but because maintenance calories fall as you lose weight, it overestimates how much you'll lose over months.

Should I recalculate as I lose weight?expand_more

Yes — as your weight decreases, your maintenance calories typically decrease too, so recalculating every few weeks keeps your target accurate rather than relying on a calculation made at your starting weight.

What is the lowest safe calorie target?expand_more

Adult guidelines commonly use about 1,200 kcal a day for women and 1,500 kcal a day for men as the lower end for a weight-loss diet without medical supervision. Very-low-calorie diets should only be followed under a healthcare provider's care.