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§ 01 / TOOL

20:4 · 2:00 PM start.

STATUS ACTIVEPROTOCOLS 5LATENCY <1MS
> INPUT
PROTOCOL
EATING STARTS AT
24-HR · HHMM
2:00 PM

YOUR SCHEDULE.

20:4
// EATING WINDOW
2:00 PM → 6:00 PM
// FAST
6:00 PM → 2:00 PM
// DURATION
4h eat · 20h fast
// 24-HOUR TIMELINE
▼ EAT
12 AM6 AM12 PM6 PM12 AM
// PROTOCOL
20:4 · eat 4h · fast 20h
On a 20:4 schedule starting at 2:00 PM, your eating window is 2:00 PM → 6:00 PM and your fasting window runs 6:00 PM → 2:00 PM.
§ 02 / ABOUT

How to use this.

Intermittent fasting is eating within a fixed window and not eating outside it. The protocol you pick — 16:8, 18:6, 20:4, or OMAD — names the split: 16 hours fasting and 8 hours eating for 16:8, and so on. All protocols total 24 hours.

This tool answers the practical question: given a protocol and the time you want to start eating, what time do you stop? And when does the fasting window end tomorrow? The 24-hour timeline below the result shows it visually — neon blocks are eating hours, black blocks are fasting.

// PICKING A PROTOCOL

  • 14:10 — gentle intro, barely noticeable day to day. Skip breakfast or finish dinner early.
  • 16:8 — the standard. Most research, most adherents, easiest to maintain long-term. Usually skips breakfast.
  • 18:6 — tighter. Good for people who plateaued on 16:8 or who eat large dinners.
  • 20:4 (Warrior) — aggressive. One small meal + one big meal in a 4-hour window. Best for experienced fasters.
  • OMAD — one meal a day. High on discipline, low on time-in-kitchen. Many use it intermittently rather than daily.

// CALORIES STILL MATTER

Intermittent fasting doesn’t create a magic metabolic window. It’s a tool for controlling calorie intake — compressed eating tends to lead to eating less. If you eat 3,000 calories in 8 hours, you won’t lose weight. Pair this tool with the TDEE calculator and Macros calculator to set the underlying targets.

// WHAT BREAKS A FAST

Zero-calorie drinks are safe — black coffee, tea, water. Anything with calories breaks the fast because it triggers insulin. The "bulletproof coffee" crowd will argue, but strictly speaking, butter in coffee breaks a metabolic fast.

§ 03 / FAQ

Questions. Answered.

What do the numbers in 16:8 mean?+
The first number is hours of fasting; the second is hours of eating. 16:8 = 16 hours fasting, 8 hours eating. 18:6 = 18 fasting, 6 eating. OMAD ("one meal a day") is typically 23:1. The fast and eat hours always add up to 24.
When should my eating window start?+
Whenever it fits your life. Popular picks: 12:00 PM (skip breakfast, finish dinner by 8 PM) or 10:00 AM (breakfast-to-late-afternoon). Evening eaters can start at 5–6 PM and stop by bedtime. Consistency matters more than timing — pick a window you can hold every day.
Does coffee break a fast?+
Black coffee, tea, and water do not. Anything with calories — milk, cream, sugar, sweeteners with calories — breaks the fast by triggering insulin. If you want to be strict, stick to zero-calorie drinks during fasting hours.
Is 16:8 better than 18:6?+
Depends on your goals and tolerance. 16:8 is easier to sustain and covers most of the metabolic benefits. 18:6 and 20:4 squeeze the window tighter — useful for people who plateau on 16:8 or eat out often in the evening. OMAD is aggressive and better short-term than as a permanent lifestyle.
Can I do this every day?+
Yes — and most studies use daily protocols. A minority of practitioners do 5:2 (five normal days, two fasting days) instead. Listen to your body: if training performance drops, sleep gets worse, or cycles get disrupted, dial back.
Is intermittent fasting magic?+
No. It creates a calorie deficit by compressing eating time, but the deficit is what drives fat loss, not the timing itself. If you cram the same number of calories into 8 hours that you used to eat over 16, you won't lose weight. Fasting is a tool for controlling calorie intake, not a metabolic cheat.
§ 04 / TOOLS

Related calculators.

§ 05 / READING

Deeper dives.

20:4 fasting window starting at 2:00 PM · Krill Kits