In an industry where product specifications come with both imperial and metric numbers - it can become an arduous task to figure out, especially when you're on-site. And working in the oil and gas industry, it's certainly important to get the numbers right.

That is why we have researched and found the best unit conversion apps available for Apple, Android and Windows phones. Here's our Top of the Apps:

Apple Devices

Convert Units for Free

• Cost: Free
• Customer Rating: 4.5 stars (529 ratings)
• Description: The number one unit conversion app on iTunes is worth a download. Now in version 6.1, the app measures a variable amount of conversions including temperature, volume and speed. There is also a currency conversion built-in for those holidays away during the summer. Download >>

Convertbot

• Cost: $1.99
• Customer Rating: 4 stars (725 ratings)
• Description: This is a really slick app with a great dial feature allowing for conversions to be made quick. Features length, mass, time and loads more conversion groups. Download >>

Varel Oil & Gas Calculator

• Cost: Free
• Customer Rating: No ratings
• Description: Allowing you to instantly calculate drilling costs or air pressure and flow rates, this app will work in both the field and in the office. The app accepts both standard and metric inputs and is really easy to use. Download >>

Android Devices

ConvertPad - Unit Converter

• Cost: Free
• Customer Rating: 4.25 stars (71,653 ratings)
• Description: 10,000,000 downloads is not to be sniffed at. Featuring country specific conversions and a calculator too, this conversion app is thorough and everything you need for working out those difficult sums. Download >>

Engineering Unit Converter

• Cost: Free
• Customer Rating: 4.4 stars (1,547 ratings)
• Description: This app could be described as the 'next level up' in terms of conversions. Requiring now internet access, this app can work out physical constants, angular velocity and coordinates too - as well as the regular length and volume conversions. Download >>

Windows Devices

Convert Units & Currency HD

• Cost: Free
• Customer Rating: 4.5 stars (68 ratings)
• Description: A crisp looking app converting temperature, distance, area, weight, currencies and more. One of the best interfaces of all the apps reviewed and the ability to upgrade to save your favourite conversions on the app home screen. Download >>

Multipurpose Converter

• Cost: £0.79
• Customer Rating: No ratings
• Description: Surprisingly no ratings but definetely worth a look. With a simple layout and the ability to convert area, speed, weight, energy, concentration and power, this app could be a really useful allie for working out those quick sums. Download >>