← Estimating process

Estimating process

Taking off construction quantities.

Taking off is the systematic measurement of quantities from drawings and specifications. It is the most critical step in producing an accurate estimate — if the quantities are wrong, the estimate cannot be right.

Who this guide is for

Estimators learning measurement skills, quantity surveyors preparing bills of quantities, and contractors who need to check their own quantity take-offs.

Measurement rules

The UK uses standard methods of measurement (NRM2 or SMM7). These define how each item should be measured: which dimensions to take, what to include or exclude, and the unit of measurement for each item. Following the standard ensures consistency and reduces disputes.

Miniature example

Measuring concrete in foundations: depth measured from bottom of excavation to top of concrete, width from face to face of formwork, length along the centre line. For a trench 12 m long, 0.6 m wide, 0.4 m deep: 12 × 0.6 × 0.4 = 2.88 m³.

Common mistakes

• Measuring gross quantities without deducting openings for windows and doors
• Double-counting items that appear in multiple drawings
• Not recording the measurement dimension detail — impossible to check or revise later