1x or 2x: the trade-off in numbers
Every 1x-vs-2x article ends the same way: "it depends on your riding." True, but unhelpful — the trade is arithmetic, and it can be printed. Take the gravel matchup people actually shop: a GRX 48/31 double on an 11-36 against a 40-tooth single ring on a 10-45, both on 700×40 tires.
| Metric | 2x · 48/31 × 11-36 | 1x · 40t × 10-45 |
|---|---|---|
| Total range | 507% | 450% |
| Lowest gear (ratio · speed at 60 rpm) | 0.86 · 4.2 mph | 0.89 · 4.4 mph |
| Highest gear (ratio · speed at 90 rpm) | 4.36 · 32.3 mph | 4.00 · 29.6 mph |
| Gear pairings · distinct gears | 24 · 18 | 12 · 12 |
| Average jump between sprockets | 11.4% | 14.7% |
| Biggest jump | 16.7% | 20% |
| Shift at 20 mph (harder / easier) | 13.3% / 11.8% | 16.7% / 14.3% |
700×40 tires; speeds from ratio × circumference × cadence; "distinct gears" drops cross-ring pairings within 4% of each other; the 20 mph shift is from the usable gear nearest 90 rpm. Same engine as the calculator above — run your own pair.
Read it top to bottom: the single ring gives up 11% of the range, which arrives as a low gear 3% harder and a top gear 8% lower. It has half the gear pairings but not half the gears — 12 against 18 that are actually different. And the number that decides most people's satisfaction is the last row: at 20 mph, one click on the 1x moves your cadence about 16.7%; on the 2x, 13.3%. That's the whole debate, in seven rows.
What does a 500% gear range actually mean?
Range is your hardest gear divided by your easiest, times 100. A 500% drivetrain's top gear is five times its bottom gear — that's all. It says nothing about where the gears sit in between, and it isn't a count of anything. Marketing loves it because a 12-speed 10-51 cassette on one ring reaches 510% and sounds like more bike than a 2x at 450% — but the 2x got its range from two rings and tight spacing, while the 1x got it from sprockets that jump up to 20% at a time. More range on fewer sprockets always means bigger jumps. The formula can't hide that; the headline number does.
For a single ring the ring cancels out: range = largest sprocket ÷ smallest sprocket. A 10-45 is 450%, a 10-51 is 510%, whatever the chainring — the ring only slides the whole range up or down. For a double, multiply the chainring spread in too: (big ring ÷ smallest cog) ÷ (small ring ÷ largest cog). The 48/31 × 11-36 above is (48 ÷ 11) ÷ (31 ÷ 36) = 4.36 ÷ 0.86 = 507%. For a 1x to reach that on a 10-tooth small cog, the big cog would have to be a 51 — a mountain-bike cassette, with a mountain-bike derailleur to run it.
Does a 1x have bigger jumps between gears?
Yes, and the right way to size the jump is at the speed you hold most, not at the ends of the cassette. Every drivetrain has a gear that puts 20 mph near 90 rpm; the question is what one shift from that gear does to your cadence:
| Drivetrain | Gear at 20 mph | One click harder | One click easier |
|---|---|---|---|
| 2x gravel · 48/31 × 11-36 | 48×17 · 86 rpm | 13.3% → 76 rpm | 11.8% → 96 rpm |
| 1x gravel · 40t × 10-45 | 40×14 · 85 rpm | 16.7% → 73 rpm | 14.3% → 97 rpm |
| 2x road · 50/34 × 11-30 | 50×17 · 86 rpm | 6.3% → 81 rpm | 11.8% → 96 rpm |
| 1x road · 44t × 10-36 | 44×15 · 86 rpm | 15.4% → 74 rpm | 13.3% → 97 rpm |
Gravel rows on 700×40, road rows on 700×28; the "usable" gear nearest 90 rpm, excluding the two most cross-chained cogs on each ring of a double. Cadence after the shift = cadence before ÷ (1 + jump).
The road compact is the striking row: with a 16-tooth sprocket in the cassette, shifting harder from the 20 mph gear costs 6.3% — 86 to 81 rpm, barely a change of breathing. The road 1x takes the same shift at 15.4%. Neither is unrideable; the difference is whether you can find the "right" gear on a false flat or have to choose between spinning slightly too fast and grinding slightly too slow. Riders who hate 1x are usually describing that gear, not the top or bottom of the cassette. If your riding is mostly steady pavement speed, that row is the one to weigh; if it's mostly climbing and descending, jumps matter far less — you're rarely hunting for a precise cadence at 6 mph.
How many gears does a 2x really have?
Not 24. On the 48/31 × 11-36, 6 of the 24 pairings land within 4% of a gear on the other ring — closer than one cassette step, so they're the same gear reached two ways. That leaves 18 distinct gears against the 1x's 12. The duplication isn't a flaw: it's why a double lets you cruise in either ring without losing a cadence, and why the front shift feels like a "reset" rather than a jump. But it means the marketing count is inflated on both sides — "24-speed" overstates the double, and "500%" flatters the single. The full gear chart shows every pairing so you can see the duplicates for yourself.
Can a 1x match a 2x's low gear?
One end or the other — not both, unless you change the cassette. On the 10-45, a 39-tooth ring reproduces the double's 31×36 climbing gear (within 1%) and gives up 11% at the top: 48×11 becomes 39×10, which at 90 rpm is spun out around 29 mph instead of 32. A 44-tooth ring keeps the top end and makes the lowest gear 14% harder — the difference between sitting and standing on the steep pitch. The calculator prints this line for any pair where one side is a single ring, so the question "which ring do I buy?" gets an actual number instead of "40 or 42 is popular."
How much weight does 1x save, and does it matter?
Dropping to a single ring removes the front derailleur, its cable, the left shifter's mechanism and the inner ring — call it 250 g, about what a full bottle weighs when it's a third empty. Run through the physics engine, a 250 W rider on Old La Honda (5.4 km at 7.3%) takes 24:20 and saves 4 seconds with those grams gone. Real, and about the same as a slightly better warm-up. The real case for 1x is simplicity and chain security in mud, not weight — the wheel weight calculator prices any grams you like the same way.
So which should you ride?
Match the drivetrain to the row of the table you'll live in.
| Your riding | Lean | Why, in the numbers |
|---|---|---|
| Fast group rides, rolling pavement, racing | 2x | The 13.3%-vs-16.7% cruising shift; a top gear you'll use |
| Mixed gravel with real climbs | Either | 507% vs 450% — pick the ring that matches the end you'll notice |
| Technical trail, mud, bikepacking simplicity | 1x | Chain retention and one fewer thing to break; a 10-51 buys the range back |
| Big mountains, loaded | 2x, or 1x on an MTB cassette | You need the 31×36-class low gear; a 1x reaches it with a 39t and loses 11% top end you won't miss |
| Flat commuting | 1x | Range is irrelevant; the jumps only bite at a cadence you're not chasing |
Numbers from the gravel pair above; substitute your own with the calculator. "Lean" is a starting point, not a verdict — the same engine can't tell you how much you dislike front derailleurs.
Two things the numbers don't show. A single ring runs the chain at a steeper angle in its top and bottom gears, which costs a few watts and some chain life at the extremes — small, but real if you live in the 10-tooth. And a double's extra range is only useful if you'll shift the front: riders who never leave the big ring are running an expensive 1x with a worse chainline. If you're weighing two cassettes on the same rings, that's the cassette comparison; if it's two doubles (50/34 against 52/36), the chainring comparison puts them side by side on your cassette.