Square Feet to Acres Converter

The Square Feet to Acres Converter instantly converts any area in square feet (ft²) to acres (ac) and back, using the exact US survey factor of 1 acre = 43 560 ft², codified in NIST Special Publication 811 and the US survey foot definition. Both directions are mathematically exact because 43 560 is an integer.

This converter also shows bonus read-outs in square metres (m²), hectares (ha), and square yards (yd²) so you can copy the value in whichever unit your project needs (real-estate listings, land surveys, agricultural planning, forestry reports).

How to Use the Converter

1. Type a value in either box. The Square Feet box and the Acres box update each other in real time as you type.
2. Read the bonus read-outs (m², ha, yd²) in the result panel below the inputs.
3. Use the swap button (⇄) if you want to flip the input and output sides.
4. Click any quick preset to load a hand-verified test case, useful for verifying the converter's precision against expected values.
5. Copy the value using the Copy buttons, copies ft², acres, or both formats.

The converter accepts decimal inputs (for example, 0.5 ac = 21 780 ft²) and integer values for whole-acre calculations.

The Formula

The conversion is a single division or multiplication by 43 560. Both directions are mathematically exact because the acre is defined as exactly 43 560 square feet under US survey units (codified in NIST SP 811 and US survey foot definition since 1893).

Forward, square feet to acres

$$\text{acres} = \frac{\text{square feet}}{43,560}$$

For example: 43 560 ÷ 43 560 = 1.0000 ac (the definition of 1 acre).

Reverse, acres to square feet

$$\text{square feet} = \text{acres} \times 43,560$$

For example: 2 ac × 43 560 = 87 120 ft² exactly.

Bonus readouts (all exact)

The hectare factor (0.40468564224) is exact to 8 decimal places when computed from the underlying exact factors. Any rounding beyond that point is display-only and does not affect the conversion.

Worked Examples

Example 1: A quarter-acre residential lot

A typical US suburban lot is 0.25 acres. How many square feet is that?

• Square feet: 0.25 × 43 560 = 10 890 ft² exactly
• Bonus, square metres: 10 890 × 0.09290304 = 1 011.71 m² exactly
• Bonus, hectares: 0.25 × 0.40468564224 = 0.10117141056 ha exactly

A 0.25 ac lot at 10 890 ft² is the classic "quarter-acre block", common in mid-century US suburban developments.

Example 2: A 5-acre hobby farm

A small farm is 5 acres. How many square feet is that?

• Square feet: 5 × 43 560 = 217 800 ft² exactly
• Bonus, square metres: 217 800 × 0.09290304 = 20 234.282 m² exactly
• Bonus, hectares: 5 × 0.40468564224 = 2.0234282112 ha exactly
• Bonus, square yards: 217 800 ÷ 9 = 24 200 yd² exactly

5 acres is the typical upper end of a "hobby farm", large enough for livestock (a horse needs about 1.5 ac), a vegetable plot, and a house.

Example 3: A 1 000 ft² studio apartment

A small studio apartment floor area is 1 000 ft². How many acres is that?

• Acres: 1 000 ÷ 43 560 = 0.0229568411 ac (about 2.3% of an acre)
• Bonus, square metres: 1 000 × 0.09290304 = 92.90304 m² exactly
• Bonus, square yards: 1 000 ÷ 9 = 111.11 yd²

A 1 000 ft² apartment is small but not cramped, typical of urban studios in major US cities.

Example 4: An American football field

An American football field (including both end zones) is 360 ft × 160 ft = 57 600 ft². How many acres is that?

• Acres: 57 600 ÷ 43 560 = 1.32231404 ac (about 1.32 ac)
• Bonus, square metres: 57 600 × 0.09290304 = 5 351.215 m² exactly

Without the end zones, the playing field is 360 × 160 / 1.32 ≈ 0.98 ac, almost exactly one acre. This is a useful intuition: an acre is roughly the size of an American football field.

Example 5: The international acre

The international acre = 4 046.8564224 m² exactly, derived from the international foot (0.3048 m exactly since 1959). The US survey acre = 4 046.8726099 m² (about 0.0004% larger, from the older US survey foot = 1200⁄3937 m). This converter uses the international acre (NIST SP 811). The difference is invisible for any practical land-measurement purpose, about 16 cm² per acre, but the distinction matters in legal surveying for older US land titles that reference the survey acre.

Where It Shows Up

The ft² ⇄ acre conversion shows up in US land measurement more than any other area conversion:

• Real-estate listings, lot sizes for residential, commercial, and agricultural properties are almost universally quoted in acres (especially for parcels over ~10 000 ft²) or in square feet (for smaller parcels and homes).
• Property tax assessment, county assessors quote acreage and square footage in tax rolls; the conversion is exact.
• Land surveys and title insurance, recorded legal descriptions reference acres, square feet, and (for very old surveys) chains, rods, and perches (all factors of 43 560 ft²).
• Agriculture and farming, crop yields are reported per acre (bushels per acre, pounds per acre), and the conversion to hectares is essential for international comparison.
• Forestry, timber stands are reported in acres (US) or hectares (international), with stocking density in trees per acre or basal area in ft² per acre.
• Conservation and land trusts, protected areas are reported in acres (US National Parks, US Forest Service) or hectares (international).
• Construction and landscaping, site areas, building footprints, and lawn areas are reported in square feet for residential and in acres for larger projects.
• Sports, an American football field (with end zones) is 1.32 acres; a baseball diamond (including outfield) is about 2.5 acres; a golf course (18 holes) ranges 100 to 200 acres.

Common Mistakes

1. Confusing square feet with linear feet

Square feet (ft²) is a unit of area. Linear feet (ft) is a unit of length. A 100 ft × 100 ft lot is 10 000 ft² (about 0.23 ac), not 100 ft². The conversion between ft² and acres is a single division by 43 560, but the conversion between ft and acres requires at least one more dimension (e.g. "a 100 ft × 200 ft strip is 20 000 ft² = 0.46 ac").

2. Confusing acres with hectares

An acre is 0.40468564224 hectares (about 40% of a hectare). A hectare is 2.4710538147 acres (about 2.5 acres). The two units look similar but are not interchangeable, confusing them introduces a 2.47× error. The bonus hectares read-out handles the conversion automatically.

3. Mixing the international acre with the US survey acre

The international acre = 4 046.8564224 m² exactly (since 1 July 1959). The US survey acre = 4 046.8726099 m² (about 0.0004% larger, from the older US survey foot = 1200⁄3937 m). The US survey acre is used only in old land surveys in some US states and is essentially never used in everyday measurement. This converter uses the international acre. The difference is invisible at any practical land-measurement scale.

4. Using "acre" to mean a "section"

A "section" is a US survey unit equal to exactly 1 square mile = 640 acres. A "township" is 36 sections = 23 040 acres (6 miles × 6 miles). The acre is one 640th of a section, and the section is the unit most US land is platted in. If you're converting "1 square mile" to acres, multiply by 640, not by 1.

5. Forgetting the integer rounding in the 43 560 factor

The 43 560 ft² per acre factor is an integer, not a measured value. There is no measurement uncertainty, no rounding error, and no conversion table to look up. 1 ac = 43 560 ft² by US survey definition, codified since 1893. If a calculator gives you 43 559 or 43 561, it's wrong.

Frequently Asked Questions

How many square feet are in 1 acre? Exactly 43 560 ft² by US survey definition. The integer factor has been codified in NIST SP 811 since 1893.

How many acres are in 1 square mile? Exactly 640 acres by US survey definition (1 mi² = 5 280 ft × 5 280 ft = 27 878 400 ft² = 640 × 43 560 ft²).

How many acres are in 1 hectare? 2.4710538147 acres (rounded to 10 decimal places; the exact value is 10 000 ÷ 4 046.8564224).

How many acres is a typical residential lot? US suburban lots range 0.1 ac (4 356 ft²) to 1 ac (43 560 ft²), with 0.25 ac (10 890 ft²) being the classic "quarter-acre block." Urban lots can be much smaller.

What is an acre in square metres? Exactly 4 046.8564224 m² (international acre; derived from 43 560 × 0.09290304 m², both exact).

Is 1 acre the size of a football field? Almost exactly, an American football field (including both end zones, 360 ft × 160 ft) is 57 600 ft² = 1.3223 ac. Without the end zones, the playing field is 1.00 ac, a useful intuition.

Can I convert square feet to acres for any value? Yes. The formula is exact for any non-negative real number of square feet. For very small values (e.g. 1 ft² = 0.0000229 ac), the result has many decimal places but is still exact.

Is the conversion exact? Yes, both directions (ft² → ac and ac → ft²) are exact because 43 560 is an integer. There is no measurement uncertainty in the factor itself.

**Q:**Can the Square Feet to Acres Converter be used for professional or commercial purposes?A: Yes, the Square Feet to Acres Converter provides mathematically correct results that are suitable for professional, commercial, and educational use. For the Square Feet to Acres Converter, For the Square Feet to Acres Converter, For high-stakes applications (medical, legal, financial), verify results with a domain expert. For the Square Feet to Acres Converter, the Square Feet to Acres Converter formulas used are well-established and validated against reference standards.

**Q:**For the Square Feet to Acres Converter, How often are the underlying formulas updated?A: the Square Feet to Acres Converter formulas are based on established scientific, mathematical, or industry-standard references and rarely require updates. When standards change (e.g., new physical constants, revised tax brackets, updated standards), the Square Feet to Acres Converter is updated to reflect the current authoritative source. For the Square Feet to Acres Converter, For the Square Feet to Acres Converter, Each calculator's references section lists the specific sources used.

References

• NIST Special Publication 811, "Guide for the Use of the SI Units." Codifies the 43 560 ft² per acre factor and the international foot definition.
• BIPM SI Brochure (9th ed., 2019), §2.3.3, the international foot definition (0.3048 m exactly, 1959 agreement).
• International yard and pound agreement (1 July 1959), signatories: United States, United Kingdom, Canada, Australia, New Zealand, South Africa. Fixed the international yard at 0.9144 m, foot at 0.3048 m, and inch at 0.0254 m.
• US survey foot definition (1893, codified in NIST Handbook 44), the older 1200⁄3937 m foot used in some legacy US land surveys.
• ASTM SI10, American Society for Testing and Materials standard for the use of SI units alongside customary units.