How to check a percentage claim
To check a percentage claim, find the two underlying numbers, decide whether the claim is a percentage change, a percentage-point change or a share, and redo the sum. Many disputes come from mixing up percentage points and percentages, or from adding yearly rates instead of compounding them. The examples below use Bank of England, ONS and HM Treasury figures.
Three kinds of percentage
A share: part of a whole, such as "87% of requests were answered on time".
A percentage change: how much a number grew or shrank relative to where it started: (new − old) ÷ old × 100.
A percentage-point change: the simple difference between two percentages: new % − old %. See percentage point .
When the thing being measured is itself a percentage (an interest rate, an unemployment rate, an inflation rate), the two kinds of change give very different numbers, and both can be accurate.
Worked example 1: Bank Rate, points and per cent
On 13 October 2026 we opened the Bank of England's Official Bank Rate history . It lists Bank Rate at 5.25% from 3 August 2023 and 3.75% from 18 December 2025, and shows 3.75% as the current rate.
Percentage-point change: 3.75 − 5.25 = −1.5 percentage points .
Percentage change: −1.5 ÷ 5.25 × 100 = about −29% .
"Interest rates have fallen by 1.5 points" and "interest rates have fallen by almost 30%" describe the same change. Low starting values make the gap wider: the same table shows 0.10% from 19 March 2020 and 0.25% from 16 December 2021. That is a rise of 0.15 percentage points, which is also a 150% increase.
When you see either form, convert it to the other and ask which the speaker meant. For context on today's rate, see Bank Rate .
Source: Official Bank Rate history
Worked example 2: "inflation is falling" and prices
The ONS series for the CPI annual rate (D7G7) gives 3.8% for August 2025 and 3.1% for August 2026. The inflation rate fell by 0.7 percentage points. Prices did not fall: the CPI index (D7BT) rose from 139.3 to 143.6 over the same year.
Check: 143.6 ÷ 139.3 = 1.0309, a rise of 3.1% , which matches the published annual rate in Consumer price inflation, UK: August 2026 . Recomputing a published rate from the index is a quick way to confirm you are reading the right series.
Source: Consumer price inflation, UK: August 2026
Worked example 3: compound, do not add
HM Treasury's GDP deflator release of 1 October 2026 shows the deflator rising 3.93% in 2024-25 and 3.35% in 2025-26. Adding these gives 7.28%. The correct two-year change compounds them: 1.0393 × 1.0335 = 1.0741, or 7.41% . The index values confirm it: 93.1026 in 2023-24 to 100 in 2025-26.
The gap is small over two years and large over ten. Any claim that adds up annual percentages over a long period needs this check.
Source: GDP deflator release of 1 October 2026
Worked example 4: which total is the percentage of?
The Cabinet Office's Freedom of Information statistics: annual 2025 (published 29 April 2026) gives several percentages with different bases:
94,526 requests were received in 2025;
62,515 of these were "resolvable", and of those, 36% were granted in full;
34,807 were withheld in full or in part, and of those, 26.6% were withheld because of the cost limit.
So "36% of FOI requests were granted in full" is a percentage of resolvable requests, not of all 94,526. And 26.6% of 34,807 is about 9,260 requests refused on cost, which is about 10% of all requests received. The same release reports 87% answered in time in 2025, up from 76% in 2024: a rise of 11 percentage points, which is a 14% relative increase. Each figure is accurate; each answers a different question.
Source: Freedom of Information statistics: annual 2025
Other checks
Percentage of what? "Up 20%" needs a base: of the previous year, of a target, of a total? Find the denominator in the source.
Small numbers. A percentage on a small base can sound dramatic. The ONS mid-2025 population estimates show Wales's population changing by −0.09%, which Table 1 gives as 2,800 people. Always look for the count behind the percentage.
Rates per head. Comparing places needs rates, not totals; see rate per 100,000 .
Relative and absolute risk. "Doubles the risk" may mean from 1 in 10,000 to 2 in 10,000. See odds and risk .
Rounding. Published percentages are rounded, so recomputed values can differ in the last digit. Use the unrounded data where the source provides it.
Cash or real. A percentage rise in spending may be in cash. See cash vs real terms .
A quick routine
Find the two underlying numbers and their dates in the official source.
Decide whether the claim is a share, a percentage change or a percentage-point change.
Recalculate it.
Express it the other way too (points and per cent) and see if the claim still reads the same.
Check the base, the count behind the percentage and whether the figures are cash or real.
Checklist
Found both underlying numbers and their dates
Identified share, % change or percentage-point change
Recalculated the figure
Converted between points and per cent
Compounded multi-year rates instead of adding
Checked the base and the count behind it
Official sources used in this guide
Sources: Bank of England: Official Bank Rate history, ONS series D7G7: CPI annual rate, ONS series D7BT: CPI index, HM Treasury: GDP deflators, September 2026, ONS: Population estimates, mid-2025