Work out the drop you need for a patio, paving area or slab run in seconds. Use the quick calculator for a fast answer, then scroll down for the advanced level calculator if you want to compare gradients, work in metres or feet, or plan more accurately.
Enter your patio length, choose your unit and pick a fall ratio. The calculator will instantly show the height difference needed from one end to the other.
Place your level on the slabs; this is the gap needed at the low end to hit your target fall.
These are the conversions many people want when searching for 1 in 60 fall in mm, 1 in 80 fall in mm or 1 in 40 fall in mm.
Patio fall is the gentle slope built into paving so water runs away instead of sitting on the surface. A ratio like 1 in 60 means the level drops 1 unit vertically for every 60 units horizontally.
In practical terms, a 5 metre patio at 1 in 60 needs a total fall of about 83 mm. That is enough to encourage drainage without making the paving feel noticeably sloped underfoot.
Quick example:
Patio length: 4.8 m
Chosen fall: 1 in 60
Required drop: 80 mm
Always think about where the water is going. The aim is not just a slope, but a slope in the right direction.
For many domestic patios, 1 in 60 is a common target. A gentler 1 in 80 can work where drainage is favourable, while a steeper 1 in 40 may suit situations where stronger runoff is needed. The right answer depends on the paving, the length of the run and where the water is being taken.
This is why a patio slope calculator or paving fall calculator is useful: it turns a ratio into an actual drop in millimetres, centimetres and inches.
| Surface | Typical fall | Why it matters |
|---|---|---|
| Porcelain / smooth slabs | 1 in 80 | Smooth surface sheds water easily |
| Standard paving slabs | 1 in 60 | Good balance of drainage and comfort |
| Riven / textured stone | 1 in 40 – 1 in 50 | Uneven surface holds water more easily |
Rougher surfaces need a slightly stronger fall to prevent puddling.
If your patio falls toward a single corner, measure the diagonal (longest) distance — not just the width or length. This ensures the fall is sufficient across the entire surface and helps prevent hidden low spots.
Measure the full distance that the water will travel across the patio from the high point to the low point.
Select a ratio like 1 in 60 to suit the area, materials and drainage route you are aiming for.
Use the result to establish the height difference between ends before you lay or adjust the paving.
Use this version if you want more control. You can enter distance in metres, millimetres, feet or inches, use either a standard ratio or a percentage gradient, and compare results across several units. It is useful as a patio slope calculator, gradient calculator, fall ratio calculator or general tool to calculate fall over distance.
| Output | Value | Notes |
|---|---|---|
| Total drop | 100 mm | Difference in height from high end to low end. |
| Equivalent ratio | 1 in 60 | Useful when checking a planned or existing slope. |
| Gradient percentage | 1.67% | Percentage fall over the full horizontal run. |
| Drop per metre | 16.67 mm | Handy when marking out long runs. |
Keep this helpful and honest. These are the kinds of tools that fit the job naturally and make sense beside this calculator.
A laser level makes it much easier to transfer levels across a patio area and keep your fall consistent from one end to the other.
Ideal for larger patios, repeated checks and cleaner set-out work.
A long level is a simple way to check the slope as you go, especially when used with a straight edge and measured packing.
A good fit for smaller jobs and homeowners who want a more basic setup.
A wide rake helps level off hardcore or bedding material more evenly before final checks, making it easier to create a consistent run.
Useful for tidying and shaping the base before you set finished levels.
Always check local building regulations where required.
A commonly used target is around 1 in 60, although exact requirements can vary depending on the patio surface, surrounding levels and where the water needs to go.
Many patios are set somewhere around 1 in 60. Some can work at 1 in 80, while others need a stronger slope depending on drainage and layout.
You need enough fall to move water consistently without making the finished paving feel too steep. The correct amount depends on the run length and the surface being laid.
It can be in some situations, especially where the surface is well laid and drainage is favourable, but a slightly stronger fall may give you a better margin for error.
At 1 in 60, 5 metres needs roughly 83 mm of drop. Use the calculator above to test different ratios instantly.
1 in 60 is equal to roughly 16.7 mm of fall per metre.
1 in 80 is equal to 12.5 mm of fall per metre.
1 in 40 is equal to 25 mm of fall per metre.
In many cases, yes. The main goal is to move water safely away from the building and toward a suitable drainage route.
Yes. A fall that is too aggressive can feel awkward underfoot, look wrong and create installation issues. You want enough slope for drainage without overdoing it.
Even with an overall fall, local dips, uneven bedding, movement or poor drainage routes can still cause standing water.
If you are planning a full garden or paving job, it helps to pair your fall calculation with pricing, materials and layout tools so you can make better decisions before you start.
