Turnouts
Number 4 vs Number 6 Turnout
Quick answer
A number 4 turnout diverges at 14.25 degrees and fits tight yards and industrial spurs; a number 6 diverges at a gentler 9.53 degrees and runs mainline speed diverging moves far more smoothly. Atlas Code 83 Nickel Silver Manual Snap Switch Left HO Scale represents number 4; Atlas HO Code 83 Number 6 Left-Hand Super Switch represents number 6.
Atlas Code 83 Nickel Silver Manual Snap Switch Left HO Scale
$26.9814.25 degree frog angle, the compact choice for yards and tight industrial spurs.
Best for: sidings on a sectional track layout
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Atlas HO Code 83 Number 6 Left-Hand Super Switch
$27.409.53 degree frog angle, a gentler diverging route that suits mainline speed better.
Best for: main line and passing siding work in HO
Check price on AmazonThe verdict: a number 4 turnout is the compact choice for yards, industrial spurs and tight benchwork, while a number 6 is the smoother, more forgiving choice anywhere a train diverges at anything close to mainline speed. Turnout number describes units of travel forward for every one unit of lateral divergence, so a higher number means a longer, gentler angle, and a lower number means a shorter, sharper one.
Frog angle follows directly from that ratio: a number 4 frog angle works out to 14.25 degrees, using the formula 2 times the arctangent of 1 divided by 2 times the number. A number 6 frog angle works out to 9.53 degrees by the same formula, a noticeably gentler divergence for roughly 50 percent more length along the turnout.
On this page
- What does the "number" in a turnout number actually mean?
- How much sharper is a number 4 turnout than a number 6?
- Where does a number 4 turnout make sense to use?
- Where does a number 6 turnout make more sense than a number 4?
- Number 4 vs number 6 turnout, side by side
- Which one should you actually buy?
What does the "number" in a turnout number actually mean?
Turnout number is a ratio of units traveled forward for every one unit of lateral divergence, not an arbitrary size label. A number 4 turnout moves 4 units forward for every 1 unit sideways; a number 6 moves 6 units forward for that same 1 unit sideways, which is why a higher number produces a longer, gentler diverging route. Run the exact frog angle for any turnout number with the turnout geometry calculator.
How much sharper is a number 4 turnout than a number 6?
Using the formula frog angle equals 2 times the arctangent of 1 divided by 2 times the number, a number 4 turnout works out to a 14.25 degree frog angle, while a number 6 works out to 9.53 degrees. That is a meaningfully sharper divergence on the number 4, and equipment with longer wheelbases, particularly steam locomotives and long passenger cars, handles the number 6's gentler angle with noticeably less lurching through the frog.
Where does a number 4 turnout make sense to use?
Number 4 turnouts earn their place in yards, engine terminals and industrial spurs, where trains move slowly and the priority is packing more turnouts into a limited footprint rather than running a smooth diverging move at speed. Atlas Code 83 Nickel Silver Manual Snap Switch Left HO Scale is a common example of this compact class, sized to fit into tighter benchwork than a number 6 of the same rail code allows.
Where does a number 6 turnout make more sense than a number 4?
Anywhere a diverging route carries mainline traffic at a reasonable operating speed, or where longer equipment regularly takes the diverging route rather than only the straight one. Atlas HO Code 83 Number 6 Left-Hand Super Switch represents that use case, trading extra length for a frog angle gentle enough that a long steam locomotive or passenger car crosses it without the harsher lurch a number 4 produces at the same speed.
Number 4 vs number 6 turnout, side by side
A number 6 turnout diverges at a gentler 9.53 degrees against a number 4’s sharper 14.25 degrees, at the cost of extra length.
| Spec | Number 4 | Number 6 |
|---|---|---|
| Frog angle | 14.25° | 9.53° |
| Forward travel per unit of divergence | 4 | 6 |
| Best for | Yards, industrial spurs | Mainline diverging routes |
| Relative length | Shorter | Longer, roughly 50% more |
Frog angle uses the formula 2 times the arctangent of 1 divided by 2 times the turnout number.
Which one should you actually buy?
Buy Atlas Code 83 Nickel Silver Manual Snap Switch Left HO Scale class turnouts for yard ladders, engine terminals and industrial spurs where space matters more than diverging speed. Buy Atlas HO Code 83 Number 6 Left-Hand Super Switch class turnouts for any mainline crossover or diverging route that carries through traffic, especially with steam locomotives or longer passenger equipment. Model the actual space each choice needs with the turnout geometry calculator before finalizing a yard or mainline plan.
Frequently asked questions
What frog angle does a number 4 turnout have?
A number 4 turnout has a frog angle of 14.25 degrees, calculated as 2 times the arctangent of 1 divided by 2 times 4. That is a sharper divergence than a number 6, which is why number 4 turnouts fit into tighter spaces like yards and industrial spurs.
Is a number 6 turnout better than a number 4?
Not universally better, just different. A number 6 diverges more gently at 9.53 degrees and handles longer equipment and higher diverging speeds more smoothly, but it takes up more length along the track. A number 4 is the right choice wherever compact size matters more than diverging speed.
Can steam locomotives run through a number 4 turnout?
Generally yes at slow speeds, such as in a yard, but a number 4’s sharper 14.25 degree frog angle produces more lurching for a long steam locomotive taking the diverging route than a number 6’s gentler angle does, particularly at anything above yard speed.
How do I calculate the frog angle of any turnout number?
Frog angle equals 2 times the arctangent of 1 divided by 2 times the turnout number. A number 4 works out to 14.25 degrees and a number 6 to 9.53 degrees. Use the turnout geometry calculator to get the angle and length for any turnout number without doing the trigonometry by hand.
Do number 4 and number 6 turnouts take the same amount of space?
No. A number 6 turnout is longer than a number 4 for the same rail code, since a higher number describes a longer, gentler divergence over more distance. Check the manufacturer’s published overall length for each specific turnout before fitting one into a tight yard ladder or benchwork space.
Which turnout number should a beginner start with?
A number 6 is a safer general purpose choice for a first layout’s mainline, since it handles a wider range of equipment smoothly at reasonable speeds. Save number 4 turnouts for yard areas and industrial spurs once you know exactly what equipment needs to navigate them.
Researched, not professional advice. This page is compiled from published manufacturer specifications, instruction manuals, published NMRA standards and recommended practices, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are hobby convention rather than a standard, and they are labelled that way wherever they appear. Always check a radius, a clearance or a grade against your own equipment before you cut wood or lay rail, because manufacturers vary and so does what your specific models will tolerate. Any permanent mains wiring in a layout room is work for a licensed electrician to your local code.