How this instrument works
Two numbers that look unrelated actually share a birth certificate. A cricket pitch runs exactly 22 yards between the bowling creases — that distance is one surveyor's chain, the unit Edmund Gunter standardised in 1620 for exactly this kind of land measurement. Lay ten chains end to end and you have a furlong, 220 yards; lay a furlong by a chain — 220 yards by 22 yards — and the rectangle covers 4,840 square yards exactly. That rectangle is the acre, which is why cricket's pitch length and the acre's area both trace back to the same seventeenth-century surveying chain.
Because the international yard has been fixed at exactly 0.9144 metres since 1959, this conversion carries zero measurement uncertainty at either end: an acre is exactly 4,840 square yards by definition, and dividing 1 by 4,840 gives the 0.000206611570248 factor used here, with only its final digits ever rounded for display. The same acre also equals exactly 43,560 square feet — nine square feet to every square yard — so the two familiar figures are just the identical rectangle measured in different-sized tiles.
Square yards keep working currency in a few specific trades even where acres dominate the paperwork. Sod and turf in North America are commonly quoted and sold by the square yard, so a landscaper pricing a new lawn multiplies width by length in yards, then may need the acre figure separately for irrigation permits or municipal water-use limits. British allotment gardening runs on the same unit from the other direction: a standard full-size allotment plot is traditionally described as '10 rods, poles or perches' — about 302.5 square yards, close to one sixteenth of an acre.
- Enter the area into Square yards (yd2) — it opens at 4,840, exactly one acre, so you can see the defining case.
- Read Acres (ac) beneath it; it recalculates on every keystroke to twelve decimal places.
- For a lawn or garden plot, multiply length by width in yards first, then enter that product here.
- Working backwards from acres? Multiply by 4,840 to recover square yards exactly.
Worked example — 4,840 square yards, one acre exactly
A parcel measures 4,840 square yards, precisely one chain by one furlong. Leave Square yards (yd2) at its default and Acres (ac) reads 1.0 exactly — the definition itself doing the work, with 4,840 × 0.000206611570248 returning 1.0 with nothing left over.
Scale it down to something closer to a garden: a traditional British allotment plot of 302.5 square yards — the '10-rod' full plot long used in UK council allotment schemes — comes out to 0.0625 acre by the same factor, exactly one sixteenth of an acre, which is why allotment holders sometimes describe their plot both ways without realising the two figures are identical.
Questions
Why is a cricket pitch's length connected to the size of an acre?
Both come from the same 1620 surveying standard. Edmund Gunter fixed his measuring chain at 22 yards, and cricket's pitch — the distance between the bowling creases — was later set to that same 22-yard chain length, a unit already familiar to English land surveyors and groundskeepers. The acre, one chain by one furlong, and the cricket pitch, one chain long, are simply two different applications of the identical historical measuring tool.
Is 4,840 square yards to the acre an exact figure?
Yes, with no rounding anywhere in the definition itself. An acre is fixed as one chain (22 yards) by one furlong (220 yards), and 22 × 220 = 4,840 exactly. Because the international yard has been exactly 0.9144 metres since 1959, this figure carries no measurement uncertainty at all; only the calculator's twelfth-decimal display cut-off is ever rounded.
How many square yards are in a standard UK allotment plot?
A traditional full-size allotment plot is described as '10 rods' — rods, poles and perches being three names for the same 5.5-yard unit — which works out to about 302.5 square yards, roughly one sixteenth of an acre. Many modern council allotments are smaller half or quarter plots, but the 10-rod figure remains the historical reference size across UK allotment schemes.
How does this compare to acres measured in square feet?
They describe the identical area in different-sized tiles: one square yard equals exactly nine square feet, so 4,840 square yards and 43,560 square feet are the same acre expressed two ways. Multiply any square-yard figure by nine to get square feet, or this calculator's acre result will match either starting unit.
How big is an acre if you picture it as a square?
About 69.57 yards on each side — the square root of 4,840, an irrational number, which is itself a clue that the acre was never conceived as a square. Historically it was a long ribbon, 22 by 220 yards, shaped that way because that's how a strip of medieval ploughland actually ran.
Does the old US survey acre change this square-yard figure?
Barely, and not for long. The US survey acre was based on a survey foot fractionally longer than the international foot, making it larger by roughly two parts per million — invisible at ordinary plot sizes and only noticeable across very large tracts. NIST and NOAA officially retired the US survey foot at the end of 2022, so current conversions, including this one, use the international definition throughout.