Backyard rink calculator: board height on a sloped yard

Water always finds its level, so on a sloped yard the low end of the rink gets deep. Enter the rink size and how far the ground drops at each corner (the slope measuring guide shows how), and you get the board height for each side, the liner size, how much water it takes and how long the hose needs.

Units

Feet and inches Meters and centimeters

Length, front to back (ft) Width, left to right (ft)

Ground

Drop from a level string down to the ground at each corner (in). The highest corner has the smallest number.

Front left Front right Back left Back right

Water depth at the high end (in) Board above the water line (in) Liner past the top of the boards, each side (in) Hose flow (US gal/min)

The flow default (5 US gal/min, about 19 L/min) is a starting guess. To measure yours, time how long the hose takes to fill a 5 gallon bucket and divide 5 by the minutes.

Water needed

2,494 US gal

9,439 liters

Fill time

8 h 19 min

at the hose flow above

Deepest water

7 in

ground drop 4 in, average depth 5 in

Tallest board

9 in

liner 44 × 24 ft

Rough cost for this rink (liner, boards, brackets and water, level ground)

At each corner

Front left

Water 3 in

Board 5 in

Front right

Water 4 in

Board 6 in

Back left

Water 6 in

Board 8 in

Back right

Water 7 in

Board 9 in

Board height per side

Side	At least	Smallest lumber that covers it
Front	6 in	2x8
Back	9 in	2x10
Left	8 in	2x10
Right	9 in	2x10

The height grows evenly from one corner to the next, so a side can step down toward its high corner. Rink kit boards come in their own heights; compare them with the "at least" column.

How to measure the corners

Drive a stake at each corner of the rink. The step-by-step guide has the details. Tie a string between two stakes, level it with a line level, and measure from the string down to the ground at each stake. Keep the same string height all the way around, so all four numbers start from the same level line.

The corner with the smallest number is the high point. The calculator puts the water there at the depth you chose, and every other point gets deeper by however much lower its ground is. The ground between corners is treated as a straight slope, so bumps and dips in the middle are not counted.

Assumptions behind the numbers

The water surface is level. The water volume is the rink area times the average depth over the four corners, which is exact for ground that slopes evenly between them.
Lumber heights are the actual sizes: 2x6 is 5.5 in, 2x8 is 7.25 in, 2x10 is 9.25 in and 2x12 is 11.25 in. The warning shows when a side needs more than a 2x12. It marks the tallest single board the calculator assumes, and says nothing about strength.
Liner size is the rink plus, on each side, the tallest board height and the overhang (liner = rink + 2 × (tallest board + overhang)). The overhang is how far the liner extends past the top of the boards and is adjustable above. It is rounded up to the next whole foot (or 10 cm). Liners are sold in fixed sizes, so pick the next size up.
Fill time is the volume divided by the hose flow. Water pressure varies a lot between houses, so a bucket test gives a better number than the default.
Ice takes up about 9% more room than the water it froze from. The numbers here are for liquid water.

Guides

How much water a backyard rink needs, with gallons and fill times for common sizes.
Building a rink on a sloped yard: board heights for each drop and what to do about the deep end.
Backyard rink board height: how tall boards need to be, and what a slope adds.
What a backyard rink costs: liner, boards, brackets and water for your size, with editable prices.
Boards materials list: how many boards and stakes your rink size needs.
What size backyard rink to build: sizes for kids, skating and hockey, with water, liner and board counts.
Rink liner size chart for common rink sizes and board heights.
Liner thickness: 6 mil or 10 mil, and white or clear.
When to start a backyard rink: boards, liner and first flood, with cited temperature thresholds and a forecast check.
Flooding a backyard rink: the first fill and the thin top floods after it.
How to resurface a backyard rink: a PVC and towel resurfacer, parts list and the water for one pass.
How long a backyard rink takes to freeze: forecast rules of thumb and a best-case table by depth and temperature.
Will a backyard rink kill my grass? What the sources say about lawns under a liner, a take-down checklist and a days-under-cover counter.
How to measure slope for a backyard rink: string, line level and four corner readings.