Estimating productivity to secure more work

Estimating productivity and constants

It is essential to understand labour estimating productivity when pricing projects to secure more work and ensure you don’t lose profit. There is a fine line between profit and loss in construction when margins are so tight.

When estimating labour costs, you must know how long a task will take.

You can do this using construction experience and knowledge or a table of constants.

Using experience for estimating productivity


As a joiner, I know how long it took me to fit a 125mm x 45mm door casing. I could fit five per day. With a labour rate of £24 per hour x 8 = £192/5 door frames = £38.40 each

£38.40/5m (5m a door frame) = £7.68m

Using constants

The Labour constant for the example above is calculated by dividing the rate per m by the hourly rate.

The constant = £7.68/£24 = 0.32

To calculate the Labour rate using the constant, multiply the hourly rate by the constant.

£24 x 0.32 = £7.68

Using price books for estimating productivity and constants

I use a Spons price book to obtain constants for unfamiliar work. I don’t use the total rates as they are not accurate enough for me to price projects. 

SPONS built up rate are based on a project outside of London with a value of £4,000,000.

SPONS includes constants within the priced section. You can check the constants to make sure they work for your project, but you may want to increase them or reduce them subject to your quantities.

Other ways to obtain constants

Historical Data

  • From your company’s previous projects.
  • Same project as earlier activities.

Expert judgment

  • Project Manager.
  • Construction Manager.
  • Site Engineer.

Productivity Software

  • Productivity by Activity.
  • Activity information and Details.
  • Productivity by BOQ Item.

Search on the internet

  • The Scribe document is a simple table of labour constants. This is a paid service.

More estimating lessons

A very simple set of estimating lessons to get you started. Everything you need to know to take off quantities, then pricing them. The lessons are short and to the point. I hope you find them useful.

Mentoring Service

If you would like a one to one session on taking off quantities or pricing a project, tell me what you are looking for by completing the form below. I will make contact with you to discus a way forward.

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