Area in Bulgaria leading to hysteria?

by Measure Australia

A simple guide to common units of area measurement

In geographical and mathematical terms, ‘area’ refers to the space occupied by a two-dimensional plane. Measure Australia engages extensively with geospatial professionals regarding survey data capture, with area the most important parameter in scoping out most projects.

We usually think about area in hectares, as do most surveyors and geospatial professionals we talk to. However, it is not uniform – construction and mining sector professionals regularly refer to areas in square kilometres or even metres, and international visitors use the prevailing norms of home.

A colleague experienced this recently, while meeting a client from Bulgaria. Our team member had provided consultation for a large area LiDAR data capture, and ultimately a price had been agreed. During a later conversation, however, our colleague experienced a moment of panic when – discussing the area to be captured – the client referenced a space about ten times the area we’d quoted and prepared to capture. Palpable relief on realising a ‘dekare’ – which in practice sounds close enough to ‘hectare’ in conversation – is a unit of area measurement ten times smaller than a hectare.

This blog is a quick guide to converting common large-format area units to hectares. We include both the mathematical equivalence and a rule of thumb for approximation. In this way we hope to spare our colleague, you and the world in general from the sudden panic that can result from area confusion!

Hectare ha

10,000 m2

100 hectares = 1 km2

Example: an NRL football field is about two-thirds of a hectare, and ANZ Stadium’s (aka, Stadium Australia or Sydney Olympic Stadium) field is just over 2 hectares.
Claim to fame: the only non-SI area-unit accepted for use with the International System of Units SI


Unit name


Multiple of
next-smallest unit

Standardised to square metres m2

Convert to hectares




1 m2

Divide by 10,000 or move the decimal 4 places left



10 ca

10 m2

Divide by 1,000 or move decimal place 3 left



10 da

100 m2

Divide by 100 or move decimal 2 spaces left



10 a

1,000 m2

Divide by 10, move decimal one place left
(Are you visiting Bulgaria?)



10 daa

10,000 m2

You’re happy right here!

square kilometre


100 ha

1,000,000 m2

Multiply by 100 or move the decimal two places right


That was fairly easy – now we’ll consider units of measure of our USA friends. They do persist in using a length measurement derived from the inch. Which was solidified in its legal definition by King Edward II of England, in 1324, as the length of three grains of barley, placed end-to-end. Not the most contemporary or scalable system of measurements! Although the USA uses metric far more than most people think - including at NASA, following an unfortunate incident - 'United States customary units' (based on Imperial measures) remains the primary measurement system in common use. Along with USA, the Federated States of Micronesia, Liberia, Marshall Islands, Myanmar, Palau and Samoa use United States customary units. 

USA unit


In square metres

How many hectares

Approximate conversion to hectares



4,047 m2

0.4 ha

Divide by 2.5

Square mile


A lot


259 ha

Move the decimal two places right, and multiply by 2.5.


We trust that helps. Please contact Measure Australia regarding capture of high resolution data for mapping, land surveying purposes and all things geospatial.