Sleep debt calculator

Add up a week of short nights against what you actually need, and see how long it realistically takes to clear. Sleep is the lever most people ignore while wondering why the diet is hard.

Milo

Hours slept, each night

Mon

Tue

Wed

Thu

Fri

Sat

Sun

Your target (hours)

Your debt will appear here.

How this is worked out

The arithmetic is simple: your target multiplied by the number of nights, minus what you actually slept. What’s less simple is repayment. An extra hour doesn’t cancel an hour lost, and the recovery estimate here assumes a realistic extra 45 minutes a night rather than a heroic weekend lie-in.

Most adults need 7-9 hours. The number of people who genuinely function on six is far smaller than the number who believe they do, and the ones who are short usually can’t tell any more, because the impairment includes the ability to judge the impairment.

Why it belongs on a nutrition site: short sleep raises ghrelin and lowers leptin, so hunger rises and fullness falls. Studies restricting sleep find people eat several hundred calories more the next day without noticing. A deficit is simply harder to hold on five hours.

It also costs you in the gym. Under-slept lifters produce less force, and more of the weight lost during a deficit comes from lean mass rather than fat.

The number is the easy part

Any calculator can hand you a figure. The hard bit is the next three months: eating roughly to it, noticing when it stops working, and changing it. Milo is a coach you text like a friend. You log what you ate in a sentence, and it learns your patterns, notices when your weight stalls, and adjusts the target from what you actually did rather than from a formula.

See how Milo works

Common questions

Can I catch up at the weekend?

Partly. A long weekend sleep restores some of the alertness deficit, but it doesn’t undo everything, and it pushes your body clock later, which makes Monday harder. A consistent bedtime beats a weekly recovery.

Why does bad sleep make me hungry?

Two hormones move in the wrong direction: ghrelin, which drives appetite, rises, and leptin, which signals fullness, falls. Cravings skew towards fast carbs specifically. It’s a physiological pull, not a lack of willpower.

Do I really need eight hours?

Seven to nine covers most adults, and where you sit in that range is largely genetic. The test isn’t the number: it’s whether you wake without an alarm feeling rested, and whether you’d sleep considerably longer given the chance.

What's the single most effective change?

A consistent wake time, including at weekends. It anchors the body clock more strongly than bedtime does, and a regular wake time tends to drag bedtime earlier on its own.

Other calculators

Steps to calories — What your step count is actually worth, in calories and distance.
Water intake calculator — A daily water target from your weight and training, not '8 glasses'.
TDEE calculator — How many calories you burn in a day, and what to eat for your goal.
Calorie deficit calculator — How long a given deficit takes to reach your goal weight.
Protein calculator — Your daily protein target, based on lean mass rather than bodyweight.

These are estimates from population averages, not measurements of you. Individual metabolism varies by roughly ±10% around any formula. Nothing here is medical advice — if you have a health condition, are pregnant, or are under 18, talk to a healthcare professional before changing how you eat or train.