We're the team behind Flips, a flashcard app built around the idea of showing you a word right before you forget it. A question we hear all the time is: “I know I'm supposed to review vocabulary, but I never know exactly when to go back to a word. Today? Tomorrow? Next week?”
It's a great question, because when you review matters far more than how many times you review. Get the timing right and a word sticks with surprisingly little effort. Get it wrong and you can grind for hours and still forget. In this article we'll give you a clear answer to “when,” and show how to stop having to track it yourself.
The best time to review is just as you're about to forget
The short answer: review a word just as it's starting to slip from memory. Recalling something you still remember perfectly does almost nothing — your brain never gets the signal that the word matters. But pulling back a word you've half-forgotten takes real effort, and that effort is exactly what tells your brain to hold on to it.
This is why reviewing too early is wasteful and reviewing too late means starting over. The sweet spot is the moment of “I almost remember this.” That's when a single review does the most work.
Widen the gaps as a word gets stronger
So when is that “about to forget” moment? It keeps moving later. A word you just learned starts fading by the next day. But once you've recalled it solidly a couple of times, it'll hold for several days, then a week, then much longer before it slips again.
A reasonable rough schedule looks like this: the next day → a few days later → about a week → a few weeks → a month. Each successful recall lets you stretch the next gap wider. This is spaced repetition, and it's the way to make a memory last with the fewest total reviews. You don't go over everything every day — you return to each word at the moment it's fading.
Why you can't manage this timing by hand
Here's the practical problem. Every word fades at its own pace, and you're rarely learning just one. Tracking “this word was learned three days ago, review today; that one was last week, next week; this batch is due tomorrow…” across hundreds of words is simply not something a person can do reliably. So most people give up and review everything at once, or just study whenever they feel like it — and lose the timing entirely.
That's the exact problem we built Flips to solve. Based on the forgetting curve, Flips calculates the next ideal review time for each individual word. Answer a word correctly and its gap widens; miss it or feel unsure and it returns sooner. You never have to decide “when” — you just open the app and answer the words it brings up.
The answering itself is built around recall. In Card Mode you remember the meaning before flipping; in Quiz Mode you choose from four options with instant feedback. Both pull the answer from your own memory rather than letting you skim and feel familiar. Standard decks for English, Spanish, Chinese and more are included, you can build your own wordlist, and Flips can notify you when reviews are due so the timing never slips past you.
You don't need to figure out “when” on your own. Aim for the moment just before forgetting, widen the gaps as words get stronger — and let an app keep track of the schedule for you.
Flips
The flashcard app that shows you words right before you forget them. Review timing managed automatically by the forgetting curve. Free to start.
Learn more about FlipsFrequently Asked Questions
When is the best time to review a word?
Just as it's starting to fade. Recalling a word you still remember perfectly does little; recalling one you've half-forgotten signals to your brain that it matters and strengthens the memory the most.
How should I space my reviews?
A rough guide: the next day, then a few days, about a week, a few weeks, a month — widening the gap each time. The more solidly you've recalled a word, the longer it holds, so the gaps can keep stretching.
Why can't I just track review timing myself?
Because every word fades at its own pace, and tracking due dates for hundreds of words by hand isn't realistic. Most people end up reviewing everything at once or studying at random, losing the timing entirely.
How does Flips decide when to show each word?
It calculates the next review time per word from the forgetting curve. Correct answers widen the gap; misses bring the word back sooner. You just answer what appears, and Flips can notify you when reviews are due.