# Area converter

> Convert square feet to square metres, acres to hectares and sq ft to Indian land units (guntha, cent, bigha, marla, kanal, ground), with exact factors.

Interactive version: https://www.calcopenly.com/conversion/area-converter
Subject: Unit converters

An area unit is the square of a length unit, so its factor is the square of a length factor: 1 ft² = 0.3048² m² = 0.09290304 m² exactly. Every unit is held as a number of square metres, including the acre (43,560 ft²) and the hectare (10,000 m²), and a conversion multiplies by one factor and divides by the other.

Flat and plot sizes are the usual reason to convert. The default 1,000 ft² flat is 92.90304 m², and 1 hectare is 2.4711 acres. Indian land units are included: a guntha is 1/40 acre (1,089 ft²), a cent 1/100 acre (435.6 ft²) and a ground 2,400 ft².

The bigha has no national size. The converter uses 27,225 ft² and labels every result that involves it as approximate; the marla (272.25 ft²) and kanal (20 marla) follow the Punjab standard.

## Inputs

- **Value**: A number in the “from” unit, or with its own unit
- **From** (options: square metre (m²), square kilometre (km²), square centimetre (cm²), square millimetre (mm²), hectare (ha), are (a), acre (ac), square foot (ft²), square inch (in²), square yard (yd²), square mile (mi²), cent, guntha, bigha (Uttar Pradesh), marla, kanal, ground)
- **To** (options: square metre (m²), square kilometre (km²), square centimetre (cm²), square millimetre (mm²), hectare (ha), are (a), acre (ac), square foot (ft²), square inch (in²), square yard (yd²), square mile (mi²), cent, guntha, bigha (Uttar Pradesh), marla, kanal, ground)

## Results

- Converted value — main result
- Conversion
- Conversion factor
- Exactness

## Formula

$$
\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{m²} \end{gathered}
$$

## Worked examples

### 1000 ft² to m²

- Value: 1000 ft²
- From: square foot (ft²)
- To: square metre (m²)
- **Converted value: 92.90304 m²**
- **Exactness: Exact**
- Checked against: 1 ft² = 0.3048² m² = 0.09290304 m² (NIST HB 44 App. C); Python 3.8 fractions from the legal definitions: 290322/3125

### 1 acre in square feet

- Value: 1 ac
- From: acre (ac)
- To: square foot (ft²)
- **Converted value: 43,560 ft²**
- Checked against: NIST HB 44 App. C: 1 acre = 43,560 ft²

### 1 hectare in acres

- Value: 1 ha
- From: hectare (ha)
- To: acre (ac)
- **Converted value: 2.4710538147 ac**
- Checked against: 10,000 m² ÷ (43,560 × 0.09290304 m²) = 390625000/158080329 (Python 3.8 fractions from the legal definitions)

### 1 guntha in square feet

- Value: 1 guntha
- From: guntha
- To: square foot (ft²)
- **Converted value: 1,089 ft²**
- Checked against: 1 guntha = 1/40 acre = 43,560/40 ft² = 1,089 ft²

### Bigha varies by region (approximate)

- Value: 1 bigha
- From: bigha (Uttar Pradesh)
- To: square metre (m²)
- **Converted value: 2,529.285264 m²**
- **Exactness: Approximate**
- Checked against: 27,225 ft² × 0.09290304 m²/ft² = 2529.285264 m² (Python 3.8 fractions from the legal definitions); the bigha's size differs by district

## Questions

### How many square feet are in an acre?

Exactly 43,560 ft². An acre was historically a strip one chain (66 ft) wide and one furlong (660 ft) long, and 66 × 660 = 43,560. With the international foot of 0.3048 m that is 4,046.8564224 m², or 0.4047 hectares.

### How many acres are in a hectare?

2.4711 acres. A hectare is a 100 m × 100 m square, 10,000 m², and an acre is 4,046.8564224 m², so 10,000 ÷ 4,046.8564224 = 2.4710538 acres. In the other direction 1 acre is exactly 0.40468564224 ha.

### How do I convert square feet to square metres?

Multiply by 0.09290304, or divide by 10.7639. The factor is 0.3048², the square of the metres in a foot, so it is exact. A 12 × 15 ft room (180 ft²) is 16.72 m²; multiplying by 0.3048 instead of its square would give 54.86, more than three times too much.

### How big is a guntha, a cent and a ground?

A guntha is 1,089 ft² (101.17 m²), a square 33 ft on each side and 1/40 of an acre. A cent is 1/100 acre, 435.6 ft² (40.47 m²). A ground is 2,400 ft² (222.97 m²). All three are fixed fractions of the acre or fixed square-foot areas, so their conversions are exact.

### Why does a bigha have different sizes?

Each state, and sometimes each district, kept its own customary bigha. West Bengal and Assam use 14,400 ft² (1,600 sq yd); the pucca bigha of Rajasthan and the bigha of eastern Uttar Pradesh and Bihar are 27,225 ft² (3,025 sq yd); Himachal Pradesh uses 8,712 ft². This converter uses 27,225 ft², so check the local land record first.

### How accurate is the area converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 5 worked examples whose answers come from independent sources; for example, “1000 ft² to m²” is checked against 1 ft² = 0.3048² m² = 0.09290304 m² (NIST HB 44 App. C); Python 3.8 fractions from the legal definitions: 290322/3125.

### Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement.

## Sources

- [NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C — General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)