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IMDb, Rotten Tomatoes, Metacritic, Letterboxd and our own ten-point scale all measure different things. Convert between them and find out what a number actually means.
Choose the scale you already have a number for, type it in, and the other four update as you type. The maths is real arithmetic fitted to how each scale behaves, not a table of memorised answers.
Switch scale and the number you typed is carried across, so you never have to re-enter it.
Conversions are a guide, not a verdict. Two scales can disagree honestly, because they asked different people different questions.
The most useful thing to understand about film scores is that they are not measuring the same thing. A number from one site means very little on another until you know what question was asked, and who was asked. Rotten Tomatoes asks critics a yes-or-no question: was this worth your time? Its percentage is the share of reviews marked positive and nothing more. It is a vote, not a grade, and a vote tells you about agreement rather than intensity.
Metacritic asks for a grade. Critics submit a score out of 100, those scores are normalised onto a common scale, weighted by the publication they came from, and averaged. The result behaves far more like a quality estimate, which is why it usually sits lower than a Rotten Tomatoes percentage for the same film. A film can be 92% fresh and still hold a Metacritic in the low seventies. Both numbers are correct; they answered different questions.
Letterboxd collects half-star ratings from people who log what they watch, a self-selected and enthusiastic crowd. IMDb averages ten-point votes from an enormous, much broader audience, weighted to blunt the effect of review bombing. Our own score is neither an average nor a vote: it is a weighted rubric, five categories scored separately and added up. Four populations, four kinds of maths, and one rubric asking a different question again.
If the scales measured the same thing, converting between them would be a single multiplication. They do not, so each conversion here is a curve fitted to how that scale behaves in the wild. The steepest is Rotten Tomatoes, which needs an exponent of 1.45. That one number does a lot of work: it sends 60% positive down to about 4.8 out of ten, because a bare majority of critics saying yes is genuinely mediocre, while 90% climbs to roughly 8.6 and 100% finally reaches a perfect ten.
Metacritic is much closer to linear with an exponent of 1.20, keeping its scores near face value while still acknowledging that a Metacritic 70 reads better than a 70% anywhere else. Letterboxd runs generous, so its curve is bent at 1.35: the community hands out four stars and above only rarely. IMDb is compressed at the top with an exponent of 1.15, because a voting pool that size makes an 8.5 rare and a 9.5 almost unheard of.
Every conversion on this page is a translation, not a measurement. Turning a share of positive reviews into a degree of quality means assuming a relationship between the two, and that assumption is a judgement call rather than a law of nature. The curves hold up well across the middle of the range and drift a little at the extremes, which is what you would expect from any fitted curve.
The second reason is that the crowds behind the numbers are not the same people. A film with an arthouse release might carry forty reviews on Rotten Tomatoes and two hundred thousand votes on IMDb, and those two groups are not interchangeable. A blockbuster can attract a mass audience that rates it far more mildly than the festival crowd did. You are mapping one consensus onto another, and two consensuses do not have to agree.
That is not a flaw in the arithmetic, it is why a converter is worth having. If you know a film is 63% on Rotten Tomatoes and 7.9 on IMDb, you already know something interesting: critics were lukewarm and audiences loved it. This tool puts those numbers into one vocabulary, but the gap between them is information worth keeping.
Nothing exposes the difference between a vote and a grade better than a perfect Rotten Tomatoes score. A 100% simply means no critic filed a negative review. It can rest on thirty mildly favourable notices, which is why Rotten Tomatoes publishes an average rating beside the percentage: a film at 100% with an average of 7.4 out of ten is well liked, not transcendent.
Our curve reflects that, sending 100% to a ten but holding 60% down at 4.8 and 75% in the mid-sevens rather than treating the percentage as a straight grade. The opposite mistake is just as common. A 25% score sounds catastrophic, but if the average review is a shrug rather than a takedown, the film may be a fascinating failure rather than a waste of an evening. Read the percentage as the headline and the average as the story.
Use more than one, and treat the gap between them as the interesting part. IMDb is the best signal for popularity and plain watchability, but a million votes reward competence over ambition. Metacritic remains the strongest critic-consensus number, particularly for prestige drama, though its weighting means a handful of major outlets can move it further than you would expect.
Letterboxd is unusually good for older films, foreign-language cinema, horror and anything with a devoted niche following, because its community actually watches those things and a half-star scale lets people express mild enthusiasm. Rotten Tomatoes is the fastest answer to whether you will probably enjoy something. Just remember that a percentage is a polling result, not a review. When all four disagree, the weighted rubric behind our own score is the tiebreaker, because it asks about craft and effect rather than counting votes.
We have written the longer version of these arguments in our comparison of Rotten Tomatoes, IMDb and Letterboxd and in where Metacritic and IMDb part ways with our rubric. If you would rather read one number quickly, our guide to reading an IMDb rating explains what a 7.4 really tells you.
Pick the scale you are holding a number for, and every other scale updates as you type. The panel adds a plain-English band, from Essential down to Avoid, and the verdict line explains what the converted figure means in words.
The most useful habit is to convert two numbers rather than one: take the Rotten Tomatoes and IMDb scores for something you are weighing up, convert both, and see how far apart they land on a single scale. A wide gap is worth investigating; a narrow one usually means the consensus is solid. When you would rather make your own call, the Movie Rating Scorecard walks you through scoring a film on five weighted categories, the What Should I Watch? tool turns the decision into one button press, and if a score has you planning a whole series, the Binge-Watch Calculator will tell you how long it takes to finish.