Reverse Pro Rata Calculator
Determine the full value of a contract, subscription, or allocation based on a partial prorated amount.
What is a Reverse Pro Rata Calculation?
A reverse pro rata calculation is the mathematical process of determining the "whole" value of something when you only know the value of a specific "part" and the duration or share that part represents. While a standard pro rata calculation divides a total sum into smaller pieces based on time or ownership, the reverse method works backward from the fraction to the 100% total.
The Reverse Pro Rata Formula
To calculate the full value, we use the following formula:
Full Value = Prorated Amount / (Units Used / Total Units in Period)
Or simplified:
Full Value = (Prorated Amount × Total Units) / Units Used
Common Applications
- Employment & HR: If an employee worked 12 days in a month and was paid 2,400 units, the reverse pro rata helps determine their full monthly base salary.
- SaaS & Subscriptions: If a customer was charged 15.00 for 10 days of service, you can determine the full 30-day monthly subscription rate.
- Real Estate: Determining the annual property tax based on a partial payment made during a mid-year closing.
- Resource Management: Scaling up production costs from a pilot phase to a full production cycle.
Example Calculation
Imagine you have a consulting contract where you were paid 3,500 for 14 days of work in a month that has 31 days. To find the total value of the month if you had worked the full duration:
- Partial Amount: 3,500
- Units Used: 14
- Total Units: 31
- Calculation: (3,500 × 31) / 14 = 7,750
The total monthly value of the contract is 7,750.
Why Accuracy Matters
In financial auditing and contract management, reverse pro rata is vital for identifying errors in billing. If the "Full Value" calculated does not match the agreed-upon contract price, it indicates an error in the initial prorated calculation or an incorrect application of the "Units Used" factor (such as using business days instead of calendar days).