How Long Is a 1:12 Ramp? | Length Table by Rise and Slope Standards
When you want to add a wheelchair ramp to a step at the front door or back door, the first thing you need to know is how long it has to be. This guide covers how to work out the length from a 1:12 or 1:15 slope, a table of ramp lengths for rises from 5 cm to 1 m, the slope, width and landing rules in Japan's Barrier-Free Act and Building Standards Act, what to look for when choosing a ramp for your home, and how Japan's long-term care insurance can help with the cost.
Ramp length is “rise × n”
A 1:12 slope means you rise 1 for every 12 you travel horizontally. So the horizontal length needed to climb a step is simply the height of the step multiplied by 12. A 10 cm step needs 120 cm, a 20 cm step needs 240 cm, and a 45 cm step needs 540 cm. For 1:15 multiply by 15, and for 1:20 by 20.
This is the horizontal length along the floor. The board itself (the sloping length) is slightly longer, but at 1:12 it is only about 1.0035 times the horizontal length — less than 1 cm extra even on a 2.4 m ramp. When comparing with the space available, it is fine to think in horizontal length.
Ramp length table by step height
This table lists the horizontal length for each slope at common step heights. Under Japan's rules, 1:8 is allowed only for short ramps rising 16 cm or less, 1:12 is the mandatory standard for buildings, and 1:15 is the recommended standard outdoors.
| Step height | 1:8 (about 7.1°) | 1:12 (about 4.8°) | 1:15 (about 3.8°) | 1:20 (about 2.9°) |
|---|---|---|---|---|
| 5 cm | 40 cm | 60 cm | 75 cm | 1.0 m |
| 10 cm | 80 cm | 1.2 m | 1.5 m | 2.0 m |
| 15 cm | 1.2 m | 1.8 m | 2.25 m | 3.0 m |
| 16 cm | 1.28 m | 1.92 m | 2.4 m | 3.2 m |
| 20 cm | (not allowed) 1.6 m | 2.4 m | 3.0 m | 4.0 m |
| 30 cm | (not allowed) 2.4 m | 3.6 m | 4.5 m | 6.0 m |
| 45 cm | (not allowed) 3.6 m | 5.4 m | 6.75 m | 9.0 m |
| 60 cm | (not allowed) 4.8 m | 7.2 m | 9.0 m | 12.0 m |
| 75 cm | (not allowed) 6.0 m | 9.0 m | 11.25 m | 15.0 m |
| 100 cm | (not allowed) 8.0 m | 12.0 m + 1 landing | 15.0 m + 1 landing | 20.0 m + 1 landing |
“Not allowed” means that under Japan's Barrier-Free Act standards, 1:8 cannot be used for a rise over 16 cm. A ramp rising more than 75 cm needs a landing at least 150 cm deep for every 75 cm of rise, so climbing 1 m at 1:12 needs 12 m of ramp plus a 1.5 m landing: 13.5 m in total.
Ramp standards in Japan's Barrier-Free Act and Building Standards Act
Ramps in shops, public facilities and similar buildings in Japan are designed to the Barrier-Free Act's building accessibility standards (the mandatory standard) and the guidance standard (a higher level to aim for). The main figures are as follows.
| Item | Mandatory standard | Guidance standard |
|---|---|---|
| Slope | 1:12 or gentler (1:8 or gentler if the rise is 16 cm or less) | Indoors 1:12 or gentler, outdoors 1:15 or gentler |
| Width | 120 cm or more (90 cm or more if stairs are provided alongside) | 150 cm or more (120 cm or more if stairs are provided alongside) |
| Landings | When the rise exceeds 75 cm, a landing at least 150 cm deep every 75 cm of rise | Same |
| Handrails | Where the slope is steeper than 1:12, or where the rise exceeds 16 cm and the slope is steeper than 1:20 | On both sides |
Separately, the Building Standards Act Enforcement Order requires ramps used in place of stairs to be 1:8 or gentler with a rough or slip-resistant surface. A portable ramp at the front door of a house is not directly bound by these standards, but they are a useful yardstick for a safe slope. Some local governments add stricter rules by ordinance, so for work on shops or apartment buildings, check the local ordinance too. For the riser and tread rules when you climb the height with stairs instead, see how to size stair risers, treads and the number of steps.
Choosing a ramp for your home
- Self-propelled manual wheelchair: gentler than 1:12 to 1:15. If arm strength is a concern, aim for 1:20.
- Pushed by a carer: portable ramps of about 1:8 to 1:10 are a common choice. On the way down, turn the wheelchair backwards and lower it slowly.
- Power wheelchairs and mobility scooters: each model has a maximum climbing angle, so stay within the figure in the manual.
- Pushchairs, hand trucks and bicycles: about 1:8 often works, but the gentler the slope, the easier it is with a heavy load.
If there is not enough depth, you can turn the ramp back on itself partway, reduce part of the step with a platform or raised section and combine it with a shorter ramp, or use a step lift. Leave a flat space at the top and bottom of the ramp where a wheelchair can stop and turn (about 150 cm square as a guide); this also makes opening and closing doors easier.
Ramps covered by Japan's long-term care insurance
In Japan, people certified as needing support or long-term care may be able to get a ramp through long-term care insurance. Which scheme applies depends on whether building work is involved.
| Type | Scheme | Key points |
|---|---|---|
| Ramps fixed by building work, or removing a step | Home modification | Up to 200,000 yen per person (co-payment of 10–30% depending on income). You must apply to the municipality before the work |
| Portable ramps that are simply placed | Welfare equipment rental | No building work needed, and easy to swap if the person's condition changes. Some can be bought instead of rented |
In both cases, the first step is to talk to your care manager. Home modification may not be paid if you apply after the work, so check the procedure before signing a contract with a contractor.
Work out the ramp length from the step height
In the slope and angle meter (smartphone level), choose or enter the step height on the “Height, length and ramp” tab, and it lists the angle, horizontal length, number of landings and total length including landings for 1:8, 1:12, 1:15 and 1:20. To measure the slope of an existing ramp, lay the long edge of your phone along the ramp in the direction of travel and read the angle and 1/n.
For comparing in % and degrees see converting slope between percent and degrees, and for measuring with a phone and correcting its error see how to measure floor tilt with a smartphone.
FAQ
- How long is a 1:12 ramp for a 10 cm step?
- 120 cm of horizontal length. A 1:12 ramp needs 12 times the height, so 10 × 12 = 120 cm. At 1:15 it is 150 cm, and at 1:20 it is 200 cm.
- What angle is a 1:12 ramp?
- About 4.76°, or about 8.33%. 1:15 is about 3.81° (about 6.67%), and 1:8 is about 7.13° (12.5%).
- How often are landings needed?
- Under Japan's Barrier-Free Act standards, a ramp rising more than 75 cm needs a landing at least 150 cm deep for every 75 cm of rise. Climbing 1 m at 1:12 needs one landing partway.
- What slope should I choose for a portable home ramp?
- For a self-propelled wheelchair, choose something gentler than 1:12 to 1:15. When a carer pushes, about 1:8 to 1:10 is common. Choosing the gentlest ramp that fits the available length is the safest approach.
- Can long-term care insurance be used for a ramp?
- In Japan, if you are certified as needing support or care, a ramp that involves building work may be covered as home modification (up to 200,000 yen), and a portable ramp may be covered by welfare equipment rental. Talk to your care manager and the municipality before the work.
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