Methodology

This page explains exactly where every number on NaijaCalc comes from and how it is calculated. If a figure on the site is not explained here, treat it as unreliable and tell us.

The core principle

Every figure carries a source, a date, and a confidence rating.

Three confidence tiers are used:

• High — a statutory rate, a published tariff, or a figure from an official instrument. These are exact and change only when the law changes.
• Medium — a compiled figure from multiple published sources that broadly agree, such as pump prices or a salary range.
• Low — an estimate where published sources are thin, conflict, or are out of date.

Where sources disagree, the disagreement is published rather than averaged away. Rent relief under the 2026 tax law is the clearest example: some summaries put the cap at ₦500,000, others at a flat ₦200,000, so the calculator does not apply it by default.

Tax figures

The personal income tax bands come from the Fourth Schedule of the Nigeria Tax Act 2025, effective 1 January 2026:

These bands were corroborated across at least three independent sources before being published, because published summaries of the new law disagree with each other. Several widely circulated articles give the 18% band as ₦7,000,000 wide; it is ₦9,000,000.

Statutory rates used:

• Pension — 8% of pensionable emoluments (employee), 10% minimum (employer), per the Pension Reform Act.
• NHF — 2.5% of basic salary. Voluntary for private-sector employees under the 2026 Act; still mandatory in the public sector.
• National minimum wage — ₦70,000 per month, National Minimum Wage Act 2024.

Order of operations

The take-home calculation runs in this order: gross → less pension → less NHF → less rent relief → chargeable income → progressive bands → PAYE. Net pay = gross − pension − NHF − PAYE.

The Consolidated Relief Allowance is not applied, because it was abolished. For reference, the old formula was the higher of ₦200,000 or 1% of gross income, plus 20% of gross income.

Electricity tariffs

The service-based tariff framework was introduced by NERC on 1 November 2020. Band A moved to a cost-reflective rate in April 2024 and was reviewed under the MYTO order of 7 December 2025.

Band A is a national rate. Bands B to E are reference rates only — NERC approves them per distribution company, they have been frozen at December 2022 levels, and they have never converged. Band C alone runs ₦45.80 at Ikeja Electric, ₦47.57 at KEDCO, ₦53.78 at EEDC and ₦56.38 at PHED. Reported Band A rates range from ₦160 to ₦225 depending on the DisCo.

This is why the electricity calculator lets you enter your own rate, and why we tell you to read it off your vending receipt. Your receipt is the only authoritative number.

VAT of 7.5% is applied to the energy charge.

Fuel and other prices

Petrol and diesel prices are a national median compiled from several tracking sources, because there has been no single regulated pump price since deregulation. NBS state-level surveys consistently show spreads of ₦250 or more per litre between the cheapest and dearest states.

Prices are reviewed monthly. Every price field carries the range it was compiled from, so you can see how much room for error there is.

Cost-of-living indices

This is the part most worth understanding, because it is where a site like this can quietly mislead you.

We publish indices, not invented absolute prices.

Each city carries a set of indices where 100 equals the Nigerian urban median for that category. An absolute figure is then computed as:

`` city figure = national anchor × (city index ÷ 100) ``

The national anchors are:

This design matters for three reasons:

1. It survives inflation. When the naira moves, you update six anchors, not eighteen cities × six categories. The relative structure of Nigerian living costs is far more stable than the absolute numbers.
2. It is honest about uncertainty. An index says "Lagos rents run about 2.35× the national urban median." That claim is defensible. A claim that "the average one-bedroom in Lagos costs exactly ₦1,410,000" is not.
3. It is auditable. If you think Kano's rent index should be 78 rather than 85, that is a single, specific, arguable claim.

The "monthly total" quoted for each city is the annual one-bedroom rent divided by twelve, plus food, transport, data and utilities for a single adult. It deliberately excludes school fees, healthcare, generator fuel and savings — which for many households exceed the items included.

Salary data

Salary figures are compiled planning estimates, not survey results, not census averages and not offers.

They are built from published Nigerian salary surveys and job-board postings, expressed as a low–median–high monthly gross range. City figures are the national median adjusted by that city's overall cost index and rounded to the nearest ₦5,000.

Two honest caveats:

• Employers in Lagos and Abuja do pay more for the same role, but usually less than the full rent differential. Cost adjustment approximates this; it does not measure it.
• A submission pipeline exists to replace these estimates with verified reader data. Each salary page carries an invite to a pre-filled, anonymous form; submissions are validated, outlier-filtered and aggregated before any range is published. The full process, including the publication thresholds, is documented on the salary data submission guide.

Until a profession clears that threshold, treat its figures as a negotiating range rather than a market rate.

Calculator arithmetic

All calculator logic lives in one file, assets/js/calc-core.js. It runs in your browser and in the build process, so the static worked example on each page and the live result from changing an input cannot disagree.

The formulas:

• Battery sizing — watt-hours ÷ (depth of discharge × inverter efficiency) × days of autonomy
• Panel array — daily watt-hours ÷ (peak sun hours × 0.75 derate)
• Inverter size — total connected load × 1.25 surge headroom, rounded up to the next standard size
• Solar payback — capital including battery replacements ÷ (annual generator cost − annual solar maintenance)
• City equivalence — salary × (destination index ÷ origin index)

The solar payback model deliberately does not discount future cash flows. With inputs this uncertain, an NPV calculation would manufacture precision the numbers do not have.

Review cadence

Every data file records its as_of date, and the build refuses to render a page using a figure that has no source or no date.

Corrections

If a figure is wrong or stale, that is a genuine contribution. Email hello@naijacalc.ng with the figure, the source you think is correct, and the date.