How GoldC works out its numbers

Every calculation runs in your browser, using only the values you type in. Nothing is fetched from anywhere: there is no live gold price, no hidden rate, and no server that sees your numbers.

That is a deliberate limit. It means the site can never quietly show you a stale price — but it also means you supply the rate, in your own currency, from your jeweller, your bank or your own source.

Every result is an estimate. None of it is financial advice.

Part 1 below applies anywhere in the world. Part 2 covers the tools that use UK rules. Part 3 covers the four tools that depend on Indian rules. Each country's tools are grouped together so it is obvious which ones they are.

All weight units are defined from the grain, which is exactly 0.06479891 g. Every other unit is a whole number of grains, so no unit is rounded before it is used in a conversion.

Because a tola is 180 grains and a troy ounce is 480, one tola is exactly three-eighths of a troy ounce — an exact ratio, not a rounded one.

What this leaves out: some regional markets use a larger "market tola" of about 12.5 g. The converter uses the 180-grain standard, so confirm which tola your jeweller means before relying on a conversion.

A karat is one twenty-fourth of the metal, fineness is parts per thousand, and purity is the same thing as a percentage. These are international conventions: a hallmark means the same thing wherever the piece was made.

Hallmark stamps are legal grades, not exact arithmetic. 22K works out to 916.67 fineness, but jewellery is stamped 916. The converter reports the exact figure and names the stamp separately, so you can match what is on your piece. The same applies to 750 for 18K, 585 for 14K and 375 for 9K.

Rates are quoted differently in different markets — per gram, per 10 grams, per tola or per troy ounce. Enter the rate in the unit the page asks for and the arithmetic holds in any currency, because nothing here converts between currencies.

What this leaves out: dealer spreads and premiums, storage, and any tax on a gain. A dealer will rarely buy back at the quoted rate; the optional "kept back" field lets you enter a share of the value to see the result after it. The yearly return is the steady yearly rate that turns the amount paid into the value shown over the time held. It is arithmetic on your numbers, not a forecast.

Worked example — a loan of 150,000 at 10% a year over 12 months, in whatever currency you entered: EMI 13,187 a month, total repayment 158,249, of which 8,249 is interest. The page shows both plans side by side, because the monthly figure and the end-of-term figure only make sense together.

What this leaves out: processing fees, valuation charges, insurance, part-payment rules and penalties. Lenders differ, so treat this as the interest arithmetic only, not the full cost of a loan.

The ratio is the gold price divided by the silver price, both quoted in the same currency and the same unit. The page compares your result with the long-run range and describes what high and low ratios have meant historically. It makes no recommendation.

The monthly investment projection compounds a fixed monthly amount at a yearly return you choose. It is arithmetic on your assumption, not a forecast — real gold returns are not smooth, and the tool does not pretend otherwise.

Rounding happens at the display step, never in the middle of a calculation, so small differences do not accumulate. Money is shown to the whole unit or to two decimals depending on the tool; conversions keep enough decimal places to stay useful for very small weights.

Worked example — £45,000 salary, 5% sacrificed: £2,250 a year goes into the pension, income tax falls by £450.00 and National Insurance by £180.00, so take-home pay falls by £1,620.00 a year: 72p for each £1 in the pension.

Assumptions: standard tax code (1257L, S1257L in Scotland), no other income or benefits, National Insurance category A, and income tax spread evenly over the year. National Insurance and student loan are worked out on each payday's pay, as payroll does (student loan rounded down to the pound), so a bonus month is right. The same pension is also worked out as net pay and as relief at source, with HMRC's top-up for low earners and the extra relief Scottish and higher-rate taxpayers claim. From April 2029 only the first £2,000 a year of sacrificed pension stays free of National Insurance; the calculator shows that for 2026/27 rates.

What this leaves out: the self-employed, directors paid by dividends, more than one job, final salary schemes, other tax codes, car, electric car and cycle schemes, and earlier tax years. The figures are estimates; the payslip is final.

Worked example — £45,000 with a Plan 2 loan: (£3,750.00 − £2,448.75) × 9% is £117.11, rounded down to £117 a month, £1,404 a year. Taking the whole year at once would give £1,405.35; payroll works each payday on its own, so the calculator does too.

Assumptions: pay is the earnings National Insurance is charged on, as HMRC's employer specification says, so salary sacrifice lowers it and an ordinary pension contribution does not. The Lifetime view runs the loan month by month: interest by plan from the Student Loans Company's published rules, write-off at the dates GOV.UK gives, thresholds as announced or forecast by the Department for Education and otherwise rising with an RPI assumption. Future pay growth, RPI, the interest cap and the Plan 4 threshold path are this site's own assumptions, shown and editable on the page and never presented as forecasts. The Student Loans Company works interest out daily; the model works it monthly.

What this leaves out: the self-employed (Self Assessment), overseas repayment, stop notices and refunds, balances not typed by you, and policy changes not yet announced. Two jobs are worked out one job at a time, as each employer does. The figures are estimates; your payslip and your Student Loans Company statement are final.

Rules and rates are taken from primary sources, in this order of preference:

• Government and regulator publications — for the UK tool, HMRC and HM Treasury pages on gov.uk, and for the India-specific tools, PFRDA, the NPS Trust, the Department of Expenditure, the Department of Pension and Pensioners' Welfare and CBIC
• Standards bodies — hallmarking authorities, and the historic definitions behind the weight units
• Official notifications and service rules, cited with their date

Commercial articles may be used to find a rule, but never as the basis for one. If a figure cannot be traced to a primary source it is not published as fact — it is marked as an assumption, or left out.

Please report it through the contact page. A wrong figure on a money page is worth fixing quickly. Confirmed errors are corrected and the page's review date is updated so you can see it has been looked at.

How pages are written, checked and corrected is set out in the editorial policy.