Basic arithmetic
The basic calculator handles everyday addition, subtraction, multiplication, division, decimals, and percentage expressions. Type or tap an expression and see the result in the same focused panel.
Three-part calculator tools
Trefid Calculators
Input, method, result: faster answers without the clutter.
Use Trefid for quick arithmetic, date difference, and percentage calculations in one focused page. Each tool keeps the task clear: enter the values, use a simple method, and read the result without signing in.
InputsPlain fields
MethodFocused logic
ResultsReadable answers
FreeNo sign-up
Trefid 3-in-1 calculator
Inputs, method and result for everyday checks0
Date difference
Enter two dates to calculate the difference in days, weeks and approximate months.
Percentage results
Enter values above to calculate percentage-of and percentage-change results.
Three-part calculators for everyday checks
Trefid keeps common calculations close together and gives each one the same simple structure: clear inputs, focused calculation logic, and readable results.
Date difference
The date tool turns two calendar inputs into a clear span in days, weeks, and approximate months. Use the inclusive option when both the start and end date should be counted.
Percentages
The percentage tool answers two common questions: what a percentage of a number equals, and how much a value has increased or decreased between two amounts.
Why the Trefid layout works
Trefid treats calculation as a three-part task: enter the data, apply the tool's method, then read the answer. These tools are intended for quick general calculations, not professional advice.
Clear inputs
Each calculator uses plain labels and direct controls. Empty percentage fields are ignored, so you can complete only the calculation type you need.
Readable results
Date results show days, whole weeks with remaining days, and an approximate month count based on the average length of a month.
Tool coverage
- Inputs Plain values
- Method Focused logic
- Results Clear answers
- No sign-up Access
How Trefid keeps estimates useful
Every calculator is written to answer a specific practical question. The pages explain the inputs, the method, example outputs, and the main limits so a visitor can decide whether the result is suitable for a quick check or needs a more formal source.
Visible assumptions
Specialist calculators state what they include and what they leave out. For example, vehicle energy comparisons do not pretend to include depreciation, and mortgage estimates assume a fixed rate.
Review notes
Pages that use tax or repayment thresholds include review dates and source references. Household calculators point visitors back to their own tariff, bill, quote, or appliance label where those figures matter most.
Examples and checks
Worked examples show the arithmetic behind common defaults. If a calculation could affect tax, borrowing, payroll, or a large purchase, the page tells visitors to check official records or professional advice.
Private scenario tools
Solar, vehicle, mortgage, and contractor calculators now go beyond a single answer. They show a result receipt, identify the inputs that move the answer most, and let you save a few comparison scenarios in your browser without an account.
Copyable receipts
Receipts summarise the inputs, result, method, and limits. They are useful when checking a quote, comparing a tariff, or keeping a record of the assumptions used.
Scenario comparison
Save up to three versions of a calculation on supported pages. The saved scenarios stay on the device, so you can compare options without sending personal figures to Trefid.
Result drivers
Driver bars show what changes the result most, such as self-use on solar, mileage on EV costs, overpayment size on mortgages, or income assumptions for contractor take-home.
More calculators
Quick checks for household, tax, loan, and mortgage decisions where a small change can add up. Each card shows a realistic example result before you open the full calculator. For a fuller explanation of what each tool includes and leaves out, open the all calculators directory.
Energy return
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Example yearly EV savingabout £623 Open calculator Cooking energyAir fryer vs oven
Compare cooking electricity costs per use, per week, and per year.
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Example interest savedabout £46k Open calculator