How We Calculate: Methodology & Corrections Log

This page explains how the numbers on CentDaily are made, how often they change, how we round them, how to report a mistake, and how AI is used. It applies to every calculator and to most data pages. Those pages also have their own How we calculate section with the formula, assumptions and sources for that tool. The games and the crypto prices and weather pages do not have one.

Editorial standards

Published formulas. Calculators use standard, published methods, such as the loan payment formula, compound interest, and the official rules for income tax, Social Security and required minimum distributions. We explain each formula in plain words on the tool's page.
Official sources. Yearly figures such as tax brackets, contribution limits and benefit amounts come from the IRS, the Social Security Administration, the Department of Labor, the Census Bureau, the Federal Reserve and other official sources, or from respected compilations of them. Every source is linked, and the page shows the year or date the figures apply to.
No personal advice. The tools show estimates from the numbers you enter. They are not financial, tax, legal, immigration or investment advice, and they do not recommend a product, plan or provider. See the Disclaimer.
No predictions. Where a page shows an assumed future rate or return, it is labeled as an assumption you can change. We do not publish forecasts as facts.
Independence. No company pays to appear on CentDaily. See the Editorial policy.
Your data. The calculators run in your browser. What you type is not sent to CentDaily. Budgets, drafts and game progress stay on your device. See the Privacy policy.

What each "How we calculate" section contains

The formula in plain words. The main calculation, written so that you can check it by hand.
Assumptions and limits. What the tool assumes (for example a steady return, a fixed rate, the 2026 tax year) and what it leaves out (for example city taxes, fees or special cases).
Data and sources. The official documents behind the figures, the year they apply to and, for tools that use daily or weekly data, the date of the data. Pages that use only the numbers you enter say so.
Last reviewed. The date we last checked the text of that section against the tool. It is not the date of the data.

How and when figures are updated

The site is rebuilt twice a day. Daily and weekly data are downloaded automatically from their sources during each build, and each page shows the date the data applies to. Yearly rules, such as tax brackets and limits, are entered by hand from the official documents when they are published, and we review them at least once a year. Many pages say "checked on" with a date.

Figures	Official source	How often they change
Exchange rates	ExchangeRate-API (daily reference rates); European Central Bank via Frankfurter for the history chart	Daily
Treasury yields, Fed funds rate	Federal Reserve Economic Data (FRED)	Daily
Mortgage rates	Freddie Mac survey, through FRED	Weekly
Gas and diesel prices; winter heating outlook	U.S. Energy Information Administration	Weekly; the winter outlook each October
Gold and silver	gold-api.com (spot reference); World Bank Pink Sheet (monthly history)	Each build; monthly history
Inflation (CPI)	Bureau of Labor Statistics, through FRED	Monthly, after each release
Official news and release dates	IRS, Social Security, Federal Reserve, CFPB, FTC, FDIC, BLS, BEA, Census	Daily news; dates when agencies publish their schedules
Federal tax brackets, deductions, contribution limits, wage base	IRS and Social Security Administration	Once a year, after the agencies publish the next year's numbers
HSA limits, ACA subsidy percentages, I bond rates, Medicare premiums, student loan rules	IRS, Treasury, CMS, Department of Education	When the agency publishes; I bond rates change every May 1 and November 1
Social Security COLA	Social Security Administration	Announced each October
State minimum wages, sales and property tax rates	Department of Labor; Tax Foundation compilations	Checked after each January 1 and July 1 change, and when new editions come out
Rent, home values and income by state	Census Bureau, American Community Survey	Yearly, when the Census Bureau releases new estimates
Remittance prices	World Bank, Remittance Prices Worldwide	When the World Bank publishes a new edition
U.S. holidays	5 U.S.C. 6103, OPM, Federal Reserve, USPS, NYSE	Calculated from rules; rules checked when an agency changes them

If an official source has not yet published new numbers, the page keeps the last official ones and shows the year they apply to. We never replace an official figure with a guess.

Rounding and number conventions

Calculations are carried out at full precision. Only the number shown is rounded: payments and prices to the cent, larger amounts to the dollar, rates to one or two decimals, and time to whole months. A tool that adds up many small amounts, such as the tip splitter, the invoice generator and the minimum wage calculator, works in cents and rounds each line to the cent so that the parts add up to the total.
Where an official rule requires a particular rounding, the tool follows it. Examples: the Roth IRA contribution limit is rounded up to the next $10 (with a $200 minimum), the I bond composite rate is rounded to 0.01%, and the phase-outs for the tip and overtime deductions round down while the car loan interest phase-out rounds up for every $1,000 or part of it.
Because real forms, lenders and payroll systems round at other steps, a result can differ from your own paperwork by a few dollars or cents.
Money is in U.S. dollars unless the page says otherwise. Foreign amounts use the daily reference rate, not the rate a bank or card will give you.

Limits that apply to every tool

Results are estimates from the numbers you enter and the assumptions on the page. Real taxes, rates and payments depend on facts a calculator cannot see.
Rules differ by state, city, lender, employer and year. Where a tool leaves something out, such as local taxes or fees, its section says so.
For a decision with real consequences, check the official source linked on the page or ask a qualified professional.

Data reports

Besides the tools, we publish data reports: original analysis of official or openly licensed figures, such as the cost of sending money home from the U.S.. A report follows the same standards as the tools. It states the source, the year or date of the data and how the numbers were made, it computes every number from the data file with a program, it names no company, it gives no personal advice, and it offers the data as a download that others may reuse with credit. A report is a snapshot of the data period named on its page, so its numbers do not change when a tool's data are refreshed. Corrections to a report go into the log below.

Corrections policy

We want every number to be right. If you think something is wrong, write to us through the Contact page or at contact@centdaily.com and include the page address, what you expected and, if you can, the official source.

We check each report against the official source and the tool's own calculation.
We correct confirmed mistakes as quickly as we can. We do not quietly leave known errors in place.
A correction is a change to something we had wrong or left out. When it changes a number, a rule or the meaning of a result, it goes into the public log below with the date and the pages it affects. Spelling, layout and wording fixes that do not change a number are not logged.
An update is a change after an official source changed its numbers or rules, or a change in how we work. Updates that matter to readers are logged too.
Entries stay in the log. We do not remove them when the mistake has been fixed.

Corrections and updates log

October 17, 2026 Update Minimum wage by state
Minimum wage by state, January 1, 2027: added South Dakota ($12.30, tipped cash wage $6.15), announced on the state labor department page. Each announced future rate now shows its increase next to the date, and the table, the state picker and the calculator switch to a scheduled rate on its effective date by New York time. Vermont is still listed as not announced yet and Arizona's $15.65 stays marked as reported until the state's own page confirms it; no rate is estimated. No figure that was already published changed.
October 14, 2026 Correction Paycheck calculator
Corrected how we described the state payroll deductions in the paycheck calculator. The entry of 2026-10-13 below called all of them disability or paid family leave contributions. In fact the 15 states charge disability insurance, paid family leave and, in some states, employee unemployment insurance (Alaska, New Jersey, Pennsylvania) or long-term care premiums (Washington). The amounts in the calculator did not change; only the description did.
October 14, 2026 Update Methodology and corrections
Added a "How we calculate" section to every calculator and most data pages (formula in plain words, assumptions and limits, data sources, last review date; the games and the crypto prices and weather pages have none) and this methodology page with the corrections policy and this log.
October 13, 2026 Correction Paycheck calculator
Ohio: corrected the 2026 state income tax schedule (nothing owed on the first $26,050 of taxable income, then the Ohio rate table). The calculator had used a flat 2.75% from the first dollar, which overstated Ohio state tax.
October 13, 2026 Correction Paycheck calculator
Added the employee payroll contributions for state disability insurance and paid family leave in the 15 states that charge them (California, New Jersey, New York, Rhode Island, Hawaii, Washington, Massachusetts, Connecticut, Oregon, Colorado, Minnesota, Delaware, Maine, Alaska and Pennsylvania). Take-home pay had been overstated there. City taxes, which are common in some states, are shown as a reminder and are not calculated.
October 13, 2026 Correction Income tax calculator, Tax refund calculator
Child tax credit: the $2,200 credit now requires the child to have a Social Security number (and at least one parent with one). A child with only an ITIN gets the $500 credit for other dependents, which is not refundable. Before, every child under 17 received $2,200. The calculators now ask for these two facts.
October 13, 2026 Correction Income tax calculator
Senior deduction (age 65 or older, tax years 2025 to 2028): the 6% reduction for income above $75,000 ($150,000 for joint filers) is now applied separately to each person. Before, it was subtracted once from the couple's combined deduction, which overstated the deduction when both spouses are 65 or older.
October 13, 2026 Correction Social Security COLA
The Chinese page for the Social Security COLA explainer had no article text. The text has been added.
October 13, 2026 Correction HSA calculator, Medicare costs & Open Enrollment
Data sources lists: corrected source titles that were mixed with Tagalog text on the HSA and Medicare pages (for example IRS Publication 969).

How AI is used

We use AI tools to help write and test the calculators' code, to help draft the explanations and answers under each tool, and to help translate pages.
The CentDaily editorial team is responsible for what is published. Explanations are checked against the official sources they cite before they go online. Calculators are tested with automated checks and compared with the worked examples that agencies publish, where there are any.
Daily and weekly figures come straight from the official data by software, and AI does not change them. Yearly rules and figures are entered from the official documents and checked against them before they go online. The short summaries on data pages are produced from fixed templates.
Translations are made with AI tools and have not all been reviewed by a native speaker. If a translation differs from the English version, the English version controls.
We do not invent authors, experts, reviewers, reviews or testimonials. Content is published under "CentDaily editorial team".

Methodology and corrections

Editorial standards

What each "How we calculate" section contains

How and when figures are updated

Rounding and number conventions

Limits that apply to every tool

Data reports

Corrections policy

Corrections and updates log

How AI is used

The method behind each tool

Markets & investing

Home & mortgage

Taxes & pay

Retirement & savings

Loans & debt

Money & business

Creators

Travel

Weather & time